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DEPARTMENT OF THE INTERIOR.

John Barton Payne, Secretary



United States Geological Survey

George Otis Smith, Director



THE

PREPARATION OF ILLUSTRATIONS

FOR REPORTS OF THE

United STATES GEOLOGICAL SURVEY

WITH BRIEF DESCRIPTIONS OF PROCESSES

OF REPRODUCTION



BY



JOHN L. RIDGWAY




WASHINGTON

GOVERNMENT PRINTING OFFICE

1920


+==================================+
|                                  |
| THE PREPARATION OF ILLUSTRATIONS |
|                                  |
|        FOR REPORTS OF THE        |
|                                  |
| UNITED STATES GEOLOGICAL SURVEY  |
|                                  |
|                                  |
|                BY                |
|                                  |
|                                  |
|         JOHN L. RIDGWAY          |
|                                  |
+==================================+


CONTENTS.


Part I. Preparation by Authors.

                                                             Page.

  Introduction                                                  7
  Purpose and value of illustrations                            8
  Selection and approval of illustrations                       8
  Submittal of illustrations                                   10
  Kinds of illustrations                                       10
  Sizes of illustrations                                       11
  Subdivisions of plates and figures                           12
  Preparation of copy by authors                               12
    Character of original material                             12
    Preliminary preparation of maps                            13
    Material available for base maps                           14
    Basic features of maps                                     17
    Standard scales                                            18
    Orientation of maps                                        18
    Projection                                                 18
    Explanation                                                19
    Titles of maps and other illustrations                     19
    Symbols used on maps                                       20
      General features                                         20
      Letter symbols                                           20
      Oil and gas symbols                                      21
      Symbols for use on maps showing features of ground water 21
    Black-line conventions                                     23
    Materials used in preparing maps                           23
      Paper                                                    23
      Bristol board                                            24
      Tracing linen                                            24
      Inks                                                     25
      Drawing pens                                             25
      Pencils                                                  25
      Rubber erasers and cleaners                              25
      Colored pencils and crayons                              26
      Water colors                                             26
      Japanese transparent water colors                        26
    Coloring geologic maps                                     27
    Diagrams                                                   28
      Essential features                                       28
      Plans of mine workings                                   29
      Sections                                                 29
    Lithologic symbols                                         32
    Use of photographs as illustrations                        32
      Essential features                                       32
      Copyrighted photographs                                  33

      Sources of photographs                                   34
      Lending original photographs and drawings                34
      Unpublished photographs                                  34
    Specimens                                                  34
      General requirements                                     34
      Borrowed and fragile specimens                           35
      Transmittal of paleontologic specimens                   35
    Making up plates                                           36
  Reuse of illustrations                                       37
  Approval of finished illustrations                           38
  Revision of illustrations                                    38
  Submittal of proofs                                          38
  Proof-reading illustrations                                  39
  General considerations                                       39


  Part II. Preparation by Draftsmen.

  General directions                                           41
  Instruments                                                  42
  Classification of material                                   42
  Preparation of maps                                          43
    Projection                                                 43
    Details of base maps                                       45
    Transferring or copying                                    46
      Tracing                                                  46
      Celluloid transferring                                   47
      Sketching by reticulation                                47
      The "shadowless drafting table"                          47
    Topographic features                                       48
      Relief                                                   48
      Hydrography                                              51
    Cultural features                                          52
    Lettering                                                  53
      General directions                                       53
      Lettering by type                                        54
      Abbreviations                                            55
      Names of railroads                                       57
    Make-up of maps                                            57
      Forms for certain features                               57
      Border                                                   57
      Title                                                    58
      Explanation                                              58
      Graphic scales for maps                                  59
      Symbols                                                  61
      Areal patterns for black and white maps                  61
      Standard colors for geologic maps                        63
      Reduction or enlargement of maps                         63
  Diagrams                                                     64
  Sections                                                     64
  Plans and cross sections of mines                            65

  Drawings of specimens of rocks and fossils                   66
    Methods used                                               66
    Brush and pencil drawings                                  66
    Pen drawings                                               67
  Retouching photographs of specimens                          68
  Landscape drawings from poor photographs                     68
    Pen drawings made over photographs                         68
    Brush drawings from poor photographs                       69
  Outdoor sketches                                             69
  Drawings of crystals                                         70
  Retouching photographs                                       70


  Part III. Processes of Reproducing Illustrations.

  Methods employed                                             72
  Photoengraving                                               72
    General features                                           72
    Zinc etching                                               73
    Copper etching in relief                                   75
    Half-tone engraving                                        75
    Three-color half-tone process                              78
  Wax engraving (the cerotype process)                         80
  Wood engraving                                               81
  Photogelatin processes                                       82
  Lithography                                                  83
    Original process                                           83
    Photolithography                                           86
    Offset printing                                            87
    Chromolithography                                          87
    Engraving on stone and on copper                           89


  Appendix.

  Length of degrees of latitude and longitude                  91
  Metric system and equivalents                                92
  Geologic eras, periods, systems, epochs, and series          92
  Chemical elements and symbols                                93
  Greek alphabet                                               93
  Roman numerals                                               93
  Mathematical signs                                           94
  Names of rocks                                               94


ILLUSTRATIONS.

                                                           Page.

Plate   I. Methods of inserting plates and figures           10

       II. Symbols used on geologic maps, economic maps,
             and mine plans                                  20

      III. Lithologic symbols used in structure and columnar
             sections to represent different kinds of rock   32

       IV. Symbols used on base maps                         52

        V. Reduction sheet used in lettering illustrations   54

       VI. Half-tone prints showing effects produced by the
             use of six standard screens                     56

      VII. Details of the make-up of a geologic map          58

     VIII. Patterns used to show distinctions between areas
             on black and white maps                         60

       IX. Diagrams and curves                               64

Figure  1. Diagrams showing principal, guide, and auxiliary
             meridians, standard and special parallels and
             correction lines, and system of numbering
             townships, ranges, and sections                 16

        2. Conventional lines used in preparing plans and
             diagrams of mine workings to distinguish
             different levels                                29

        3. Section and perspective view showing relations
             of surface features to the different kinds of
             rocks and the structure of the beds             30

        4. Sections of coal beds                             31

        5. Diagram illustrating method of projecting a map   44

        6. Methods of expressing relief by contour lines,
             by hachures, by shading on stipple board, and
             by a brush drawing                              49

        7. Designs for bar scales                            60

        8. Method of making a bar scale for a map of
             unknown scale                                   60

        9. Map bearing six areal line patterns               62

       10. Diagram showing method of marking maps for
             reduction or enlargement (for record)           64

       11. Structure section showing method of determining
             the succession of folds                         65


THE PREPARATION OF ILLUSTRATIONS FOR REPORTS OF THE United STATES
GEOLOGICAL SURVEY.


By John L. Ridgway.




PART I. PREPARATION BY AUTHORS.




INTRODUCTION.


There has been an obvious need in the Geological Survey of a paper
devoted wholly to illustrations. No complete paper on the character,
use, and mode of preparation of illustrations has been published by
the Survey, though brief suggestions concerning certain features of
their use have been printed in connection with other suggestions
pertaining to publications. The present paper includes matter which it
is hoped will be of service to authors in their work of making up
original drafts of illustrations and to draftsmen who are using these
originals in preparing more finished drawings, but it is not a
technical treatise on drafting.

The effectiveness of illustrations does not depend entirely on good
drawings nor on good reproduction; it may be due in large part to the
inherent character of the rough material submitted. If this material
is effective or striking the finished illustrations, if well made,
will be equally effective and striking. Each step in the making of an
illustration--first the preparation of the author's original or rough
draft, next the final drawing, and last the reproduction--is closely
related to the others, and each is dependent on the others for good
results. If the material has been well handled at all three steps the
resulting illustration should be above criticism; if it has been
poorly handled at any one of the three the effectiveness of the
illustration is either impaired or ruined.

A consideration of processes of reproduction is essential in the
preparation of all illustrations, and the influence or effect of the
process to be selected on the methods of preparing a drawing has
seemed to warrant the presentation of brief descriptions of the
processes usually employed by the Geological Survey. These
descriptions include statements as to the kind of copy that is
suitable for each process, the result produced by each, and the
relative cost of the processes.


PURPOSE AND VALUE OF ILLUSTRATIONS.


An illustration in a report of the Geological Survey is not merely a
picture having a remote bearing on the subject matter of the report;
it must represent or explain something discussed or mentioned in order
to become an illustration in the true sense of the term. The
illustrations used in the Survey's reports are not employed for
embellishment; the more pictorial kinds may be in some measure
decorative, but decoration is distinctly not their primary purpose.
The illustrations used in popular literature are designed to meet a
public demand for ornament or attractiveness. Those used in scientific
publications should be made plain and direct, without attempt to
ornament or beautify. In the literature of science illustrations made
by the reproduction of photographs or of explanatory diagrams or maps
are intended simply to furnish greater illumination, and if the
illustrations display photographic reality most statements or
conclusions thus illuminated seem less open to dispute. A photograph
may thus serve the double purpose of explanation and corroboration.
The graphic expression of data and of details in a Survey report is
intended to aid the reader in comprehending the report, and this is
the prime advantage of its use, but it also enables the writer to omit
from his text numerous descriptive details. It would generally be
difficult without illustrations to present a clear picture of the
geology of a region in its exact relations, and especially to describe
adequately the form and the details of the structure of many fossils.
The tasks of both the writer and the reader of reports on geology and
kindred subjects are thus greatly facilitated by geologic maps,
sections, paleontologic drawings, and illustrations of other kinds.

The responsibility for good and effective illustrations rests largely
upon the author, who should select and plan his illustrations with a
view to their utility in aiding the reader to understand his report.




SELECTION AND APPROVAL OF ILLUSTRATIONS.


There is no rule limiting the number of illustrations that may be used
in a publication of the Geological Survey, but in selecting
illustrations for a report an author may easily fall into the error of
over-illustration. The number of diagrammatic drawings or of drawings
that express the author's deductions is rarely in excess of the needs
of a paper, but the number of photographs submitted is often
excessive. The number of pages in a manuscript may be a factor in
determining the proper number of illustrations, but as the need of
illustrations varies greatly from paper to paper this factor alone is
not decisive. The tendency to overillustrate led the Director to issue
the following order[1] governing the approval of illustrations:

[Footnote 1: From Survey Order 63, Oct. 20, 1915.]

     The primary responsibility for the selection of illustrative
     material shall rest upon the author and the chief of the
     branch transmitting the report: No one knows the subject
     matter of the report better than its author, though a
     sympathetic critic is usually needed to correct the personal
     equation that may express itself In an excessive number of
     illustrations or the use of photographs into which no one but
     the field man himself can read what he wishes to illustrate.
     The approval by the chief of branch of the illustrations
     selected by the author will be taken as vouching for those
     illustrations as essential and adequate, and the scientific
     value of the illustrations will not be subject to review in
     the section of illustrations.

     The chief of the section of illustrations shall decide the
     technical questions relating to the preparation of these
     illustrations for reproduction and may recommend the
     rejection of any that do not promise effective or economical
     reproduction. In the consideration of such questions,
     especially any relating to maps, the cooperation of the
     editor of geologic maps and chief engraver will be expected.

The judgment of an author as to the illustrative value of a photograph
is likely to be biased by his knowledge of the features that are
actually included in the view represented, not all of which may be
shown clearly in the photograph; his knowledge of all the features
enables him to see more in his picture than his readers will be able
to recognize without detailed description. Photographs in which
special or significant features are obscured by foliage or lost in
hazy distance do not make acceptable illustrations, and the use of a
picture that requires much description to make it illustrate reverses,
in a measure, the relations of text and illustrations.

A photograph is not necessarily good for reproduction simply because
it shows some particular feature to be illustrated; the quality of the
print it will afford when reproduced from an engraved plate should
also be considered. Some loss of detail by reproduction must be
expected, and therefore only the clearest and most effective prints
obtainable should be submitted.

If an author has difficulty in making his preliminary or "original"
drawings he may request that a draftsman be detailed to aid him. The
request should be made to the Director through the chief of branch and
properly approved. The work will then be done in the section of
illustrations as advance preparation, but finished drawings should not
be thus prepared unless the conditions are unusual. The administrative
geologist reviews all illustrations submitted and represents the
Director in matters relating to illustrations.


SUBMITTAL OF ILLUSTRATIONS.


All material intended for illustrations, except paleontologic
specimens, should be submitted with the manuscript of the paper to be
illustrated but in a separate package marked "Illustrations to
accompany a paper on ---- by ----." The package should contain a
carbon copy of the list of illustrations that accompanies the
manuscript or, if the titles to be printed on or with the
illustrations include fuller descriptions than are given in that list,
a carbon copy of the list giving complete titles and descriptions, the
original of which should also accompany the manuscript. In the list
each plate and figure should be separately numbered consecutively in
the order in which it should appear in the report, and a figure
opposite each title should show the number of the manuscript page on
which the illustration is first mentioned or most fully discussed.
Roman numerals should be used for the plates and arabic numerals for
the figures. Each drawing or photograph should bear, in addition to
the number and title, any suggestions concerning preparation,
reduction, and method of reproduction which the author may consider
especially desirable. The list should be headed "Illustrations."

Specimens other than fossils that are to be illustrated must be
submitted directly to the section of illustrations, but the author may
first obtain photographic prints of them in order to make up his
plates. The specimens should be carefully packed and any that are
fragile should be so marked.




KINDS OF ILLUSTRATIONS.


The illustrations in reports of the Geological Survey may be
classified into five more or less distinct groups--(1) maps, (2)
diagrams (including graphs, sections, plans, figures of apparatus, and
stereograms), (3) outdoor photographs, (4) photographs and drawings of
specimens, and (5) sketches. These may be further divided into two
large groups, which may be called permanent and ephemeral. The
permanent group includes illustrations that do not lose value through
lapse of time or by natural alteration, such as detailed geologic
maps, well-prepared structure sections, views of specimens, and good
photographs or drawings of natural phenomena; the ephemeral group
includes maps showing progress, key maps, diagrams showing yearly
production, and many others that should be prepared in such a way as
to minimize cost of preparation and reproduction.

[Illustration: U. S. GEOLOGICAL SURVEY PREPARATION OF ILLUSTRATIONS
PLATE I


METHODS OF INSERTING PLATES AND FIGURES.

1, 2, 3, 5, 6, 7, plates; 4, 8, 9, 10, figures; 11, pocket.]

The illustrations will be finally divided into plates and figures when
they are fully prepared, but if an author desires to determine the
classification in advance of transmittal he should submit his material
to the section of illustrations, where methods, processes, and
reductions will be decided for each. In determining which shall be
plates and which shall be figures, size and method of reproduction are
the only factors to be considered; there are no other real
differences. Illustrations that require separate or special printing,
such as those reproduced by Lithography and by the photogravure,
photogelatin, and three-color processes, must be printed separately
from the text as plates and inserted in the report at the proper
places; those that are reproduced by relief processes, such as zinc
and copper etching and wax engraving, if not too large, can be printed
with the text as figures. If an illustration to be reproduced by a
relief process is marked for reduction to a size not exceeding that of
the page of the text, it can be called a figure and be printed with
the text. Half tones, though etched in relief, are rarely made text
figures in Survey reports, because to give satisfactory impressions
they must be printed on the best quality of coated paper, which is not
used for the text. By using the coarser screens shown in Plate VI (p.
56), however, a half-tone cut may be made that can be used in the text
if it is smaller than the page.




SIZES OF ILLUSTRATIONS.


The regular book publications of the Geological Survey are issued in
three sizes--(1) octavo (annual reports of the Director, statistical
reports on mineral resources, bulletins, and water-supply papers); (2)
quarto (professional papers and monographs); (3) folio (geologic
folios). The following table gives the measure of the text of each
size and the measure of the trimmed page, in inches:

               Size of text.         Size of page.

Octavo        4-3/8   by  7-15/16      5-7/8 by  9-1/8
Quarto        6-1/16  by  9-1/8        9-1/4 by 11-5/8
Folio        13-13/16 by 17-7/8       18-1/2 by 21-3/4

Most professional papers are printed in two columns of type, each 3
inches wide, and folios are printed in three columns, each 4-3/8
inches wide. A text figure in one of these publications can be made to
fit one or more columns, and it may run the full length of the text
page.

The limits of the dimensions of plates and figures, in inches, are
given in the following table. If for any reason a plate can not be
reduced to the dimensions of a page it can be folded once or more; and
if it is large and unwieldy it may be placed in a pocket on the inside
of the back cover. (See Pl. I.)

            Single-page       Plate with
               plate.        one side fold.         Text figure.

  Octavo   4-3/8 by  7-1/2  7-1/2 by  8-1/2         4-3/8      by  7-1/2
  Quarto   6     by  9      9-1/2 by 14-3/4         3 or 6     by  8-1/2
  Folio   15     by 17-1/2   ............    4-3/8 or 13-13/16 by 17-7/8

For an octavo report a single-page plate with side title should be 4
inches or less in width, and a plate with bottom title should be 7
inches or less in depth. In other words, the actual depth and width
of a single-page plate in a page of any size must depend on the number
of lines in its title, the inclusion of which should not extend the
matter much, if any, beyond the dimensions given in the table. A
difference of 1 inch or less in the width of a folding plate may
determine whether it must be folded once or twice, so that by
consulting this table an author may save expense in binding and
promote the reader's convenience in handling the plate.

A text figure (including the title) can not extend beyond the text
measure but may be of any size or shape within that measure, as shown
on Plate I, figures 4, 8, 9, 10.


SUBDIVISIONS OF PLATES AND FIGURES.

If a plate consists of two or more parts or photographs each part
should be marked with an italic capital letter--=A=, =B=, etc.--which
should be placed directly under each. If it is made up of many parts,
in the form of plates that accompany reports on paleontology, each
part should be similarly marked with an arable numeral--1, 2, 3, etc.
If a text figure is subdivided into two or more parts, each part
should be marked with a roman capital--A, B, C, etc.; and if details
of a part are to be described each detail should be marked by an
italic lower-case letter--a, 6, c, etc.




PREPARATION OF COPY BY AUTHORS.


CHARACTER OF ORIGINAL MATERIAL.

In the Geological Survey, as elsewhere, the "originals"--that is, the
original material submitted by authors for the illustration of their
reports--differ greatly in character and in degree of clearness. Some
are carefully prepared; others are rough, obscure in part, and
defective in detail. Drawings made from poor originals progress
slowly, because the draftsman spends much time in interpreting
uncertain features or in conference with the author concerning
details. An original should be perfectly clear in detail and meaning,
so that the draftsman can follow it without doubt. It should not
consist of parts that must be brought together to make a new drawing,
because the result of the combination of the parts will be uncertain
at the outset and may not prove satisfactory. Each original
illustration should be prepared with the idea that the draftsman who
will make the finished drawing will be unfamiliar with the subject and
will need definite instructions; all data should be plotted and each
figure or plate should be completely made up before it is submitted.
More or less roughly prepared originals are expected, but they should
show no uncertainty in details. Obscure features may be cleared up by
inclosing the features in penciled loops connected by a line with
notes written on the margin, such as "omit this line," "turn at an
angle of 30° from true north," "add," "cut out."


PRELIMINARY PREPARATION OF MAPS.

The base map that generally accompanies a report may be an original
field sheet or it may have been compiled from various sources by an
author and made to incorporate the results of his field work. It
should not be a collection of maps of different scales and standards
to be worked into a new map.

The source of the data shown on every original base map should be
indicated on the map, whether it is to be used as an illustration or
as a record of field work. This information is required as a permanent
record for showing the reliability of the map, for use in comparing
data, and for giving full credit to those who are responsible for the
data. An author should see that this requirement is observed in order
that proper credit may be given and should especially see that all
cooperative agreements and organizations are properly mentioned.

An original map should preferably be complete in itself. It should not
consist of several parts or sheets unless the data to be represented
are unusually complex. All elaborate or technical finish of border
lines, lettering, or like features should be left to the draftsman or
the engraver.

Base maps that involve the compilation of new data should be prepared
by either the topographic branch or the division of Alaskan mineral
resources. If a base map already published is to be reused it should
be submitted to the chief topographic engineer or to the chief of the
division of Alaskan mineral resources for approval. This procedure
will insure a single standard of geographic accuracy in maps appearing
in Survey publications.

A geologist who requires a base map that includes new topographic data
should address a request for its preparation to the chief geologist,
who, through the Director, will refer the request to the topographic
branch. The request must be accompanied by a full statement regarding
the proposed report and the time when it is likely to be submitted.
The preparation of such base maps by draftsmen in the division of
geology, the land-classification board, the water-resources branch, or
the section of illustrations has been discontinued except for the
minor adaptations provided for above.

If a report requires the preparation of a base map that includes no
new topographic data such a map must be compiled from other authentic
maps by the division or branch in which the report originates. If,
however, no draftsmen are available in that division or branch, an
arrangement can be made with any other branch--as the topographic or
publication branch--that may have draftsmen available, with the
understanding that the cost of the work shall be reimbursed to the
branch doing the work by the branch ordering it. For indicating
geologic and other data, however, an author may make use of an
authentic base map already published, and after it is reduced or
enlarged to appropriate scale by photography such a map may suffice
for transmittal with a manuscript.


MATERIAL AVAILABLE FOR BASE MAPS.

The maps already published by the Geological Survey[2] and other
Government bureaus should always be consulted when a new base is to be
compiled. The following list includes most of the maps available:

1. The Survey's regular topographic atlas sheets, published on three
scales--15-minute sheets, scale, 1:62,500; 30-minute sheets, scale,
1:125,000; 60-minute sheets, scale, 1:250,000--approximately 1 mile, 2
miles, and 4 miles to 1 inch, respectively--and its "special" maps,[2]
some of which are published on other scales. All these maps can be
used as bases for detailed geologic maps, for compiling maps on
smaller scales, and for revising other maps.

2. The United States part of the international map of the world, now
being published on the scale of 1:1,000,000 (approximately 16 miles to
1 inch). Each sheet of this map represents an area measuring 6° of
longitude and 4° of latitude. The published sheets of this map may be
used as bases for general maps. The sheets are drawn on the scale of
1:500,000, and photolithographs on this scale are available for use as
bases for geologic or other maps.

The adaptability of the 1:1,000,000 scale map to use as a base for
general geologic maps is shown in the geologic maps of the southern
peninsula of Michigan and of Indiana in Monograph 53 (Pls. IV and
VII), the map of Florida in Bulletin 60 (Pl. I), and the map of
Vermont in Water-Supply Paper 424 (Pl. I).

3. The Survey's two-sheet wall map of the United States, 49 by 76
inches, scale 1:2,500,000 (approximately 40 miles to 1 inch). Parts of
this map can be used as bases for general geologic or other maps and
as copy for index and other small diagrammatic maps. This map is
published both with and without contours.

4. Land Office maps and township plats. These maps are now being
published on a scale of 12 miles to 1 inch; they are also
photo-lithographed on one-half that scale, or 24 miles to 1 inch. The
township plats are printed on a scale of one-half mile to 1 inch. The
maps are especially useful in compiling maps in which land lines
(townships and sections) are essential, and the township plats afford
valuable detail and are useful in field work and in revising other
maps. Township and section lines should appear on all
land-classification maps published by the Survey. On maps on a scale
less than 1:250,000 only the townships should be shown; on maps on
scales greater than 1:250,000 the sections should be shown; on maps on
a scale of 1:250,000 the sections should be shown, unless their
representation will materially impair the legibility of the map, in
which case only the townships should be shown. (See fig. 1.)

5. Post-route maps, covering single States or groups of adjacent
States, published on sheets of different sizes and on scales
determined mainly by the size of the State. The map of Texas is
published on a scale of 12 miles to 1 inch, that of Virginia on a
scale of 7 miles to 1 inch, and that of West Virginia on a scale of 6
miles to 1 inch. Both the Land Office and the post-route maps are
useful for reference in compiling maps on smaller scales. Post-route
maps are especially useful for comparing and verifying the location of
cities, towns, and railroads.

6. Coast and Geodetic Survey charts, published on scales that are
governed by the area represented and the amount of detail to be shown.
These maps should always be used in compiling and correcting coast
lines.

7. Maps and charts published by the Corps of Engineers of the Army,
the Mississippi River Commission, the surveys of the Great Lakes, and
the boundary surveys. These maps are especially useful if the scale of
the map to be compiled requires considerable detail.

8. The Survey's three small base maps of the United States--(_a_) a
map 18 by 28 inches, scale 110 miles to 1 inch, which is published
both with and without contours, or with relief or hypsometric shading;
(_b_) a map 11 by 16 inches, scale 190 miles to 1 inch; (_c_) a map
7-1/2 by 12 inches, scale 260 miles to 1 inch, designed for use as a
two-page illustration in a bulletin or a water-supply paper.

9. The Century, Rand McNally & Co.'s, Cram's, Stieler's, The Times,
Johnston's Royal, and county atlases.

10. State and county maps.

11. Railroad surveys, which are useful in furnishing data for
elevations as well as for locations of towns and stations.

12. The latest national-forest maps and proclamations. It is, however,
not necessary that national forests, bird reservations, and national
monuments be shown on a map in a report unless their addition is
specially requested by the author or by the chief of the branch
submitting the report, and they should not be shown if they will
obscure other more important data.

[Footnote 2: See "Topographic maps and folios and geologic folios
published by the United States Geological Survey" (latest edition).]

[Illustration: Figure 1.--Diagrams showing principal, guide, and
auxiliary meridians, standard and special parallels and correction
lines, and system of numbering townships, ranges, and sections.]

The Survey has published numerous maps of parts of Alaska, as well as
other maps, which are available for use or reuse in its reports.
Copies of all base maps for which copper plates have been engraved by
the Survey can be obtained on requisition, and their use in a new
report will save time as well as the cost of engraving. Other maps
will be found in the Survey library, where the latest editions only
should be consulted.


BASIC FEATURES OF MAPS.

It must be remembered that "every map, whatever its scale, is a
reduction from nature and consequently must be more or less
generalized."[3] The degree of generalization in the geologic and
other detail to be shown on a map usually involves a corresponding
degree of generalization in its base. Absolutely true generalization
means the same degree of omission of detail for each kind of feature.
If a base map on a scale of 1 mile to 1 inch, prepared with the usual
detail, were placed before a camera and reduced to a scale of 16 miles
to 1 inch, the lines representing the smaller tributaries of streams
and the smaller water bodies, as well as many other features, would
probably be so greatly reduced in length as to be illegible. If from
this reduced photograph a new map were prepared, from which all
features not plainly discernible were omitted, the new map should
represent what might be called true generalization. This degree of
generalization is, however, not practicable, but unessential detail
should be systematically omitted. The amount of detail which a base
map should show is limited by its scale, by the character of the
country it represents, and by the kind of data to be shown. Coordinate
features of a topographic map should be shown with equal detail.
Detail in culture may call for detail in drainage, though relief may
be greatly generalized or entirely omitted; detail in relief may
like-wise call for detail in drainage, though culture may be more
generalized.

[Footnote 3: Gannett, Henry, A manual of topographic methods: U. S.
Geol. Survey Mon. 22, p. 107, 1893.]

If the three fundamental features of a topographic map--the culture,
the drainage, and the relief--are to be engraved or photo-lithographed
separately and printed in colors, the best results can be obtained by
drawing each feature in a separate color on one sheet unless the work
is coarse and great precision in register is not needed. The culture
should be drawn in black waterproof ink, the drainage in Prussian
blue, and the relief in burnt sienna; but care should be taken that
the colors used will photograph well. To insure a good photograph it
is usually necessary to add a little black to the blue and brown. (See
"Inks," p. 25.) The photographer will then make three negatives and
will opaque or paint out all but one of the three features on each
negative. The cost is somewhat greater than that of reproducing three
separate drawings, but the result gives more accurate register than if
the drawings were made on separate sheets, which are likely to change
in size before they are reproduced.


STANDARD SCALES.

The standard scales of the maps used in the publications of the
Geological Survey are fractions or multiples of 1:1,000,000 (see p.
14), except for a map that is reduced expressly to fit one or two
pages of a report or that is reduced horizontally or vertically to fit
the text as a small diagrammatic or index map. It should be remembered
that a map which may be serviceable for use in compiling a new map,
except as to scale, can be reduced or enlarged to the scale of the new
drawing by photography, by a pantograph, or by other means. (See p.
47.)

Maps compiled by an author should be prepared on a scale of at least
1-1/2 times and preferably twice the size of the scale used on the
published map. Maps traced on linen should be no less than twice the
size of publication. Not only is the quality of the reproduction
improved by considerable reduction, but the larger scale of the
drawing facilitates the plotting of details. It should be remembered,
however, that a linear reduction of one-half produces a map only
one-fourth the area of the original, and reduction so great may
prevent the addition of data, such as an extended note in small
letters applying to a small area on the face of a map, which would not
be legible when reduced.


ORIENTATION OF MAPS.

A map that bears no arrow indicating north is supposed to be oriented
north and south, and its title should read from west to east. If,
however, the area mapped has a general trend in one direction, as
northwest to southeast, and its squaring up by a north-south line
would leave too much blank paper, this general rule is not followed.
The border lines on such a map should conform to the general trend of
the area mapped, an arrow should show north, and the title and scale
should be placed horizontally, but the projection numbers and town
names should follow the direction of the parallels of latitude. (See
Pis. X and XII, Bull. 628; and Pis. VI, XV, and XVI, Mon. 52.)


PROJECTION.[4]

[Footnote 4: See also pp. 43-45, where the method of projecting a map
is more fully explained.]

The polyconic projection has been adopted by the Geological Survey for
its topographic atlas sheets and must be consistently used for its
other maps. If a new map is to be compiled an accurate projection
should first be constructed, and no plotting should be done on it
until the projection has been checked and found to be correct. A
projection should be checked or proved by some one other than the
person who prepared it. Next the drainage and the water areas should
be outlined; then the cultural features should be added; and finally
the relief, whether expressed by contour lines, hachures, or
shading.[5]

[Footnote 5: See pp. 49-48 for methods of tracing and transferring.]


EXPLANATION.

Under the heading "Explanation" should be placed all matter needed to
describe fully the details of an illustration, whether map, diagram,
or section, so that if the illustration became detached it would be a
complete self-explanatory unit.

The explanation of a map may be placed inside the border lines if
there is ample room for it, or it may be placed outside. The standard
arrangement for an outside explanation for geologic maps is shown, in
the geologic folios, which should be followed in general form. If
there is space within the border lines the explanation may be
appropriately arranged therein, either in a vertical column or
horizontally, according to the size and shape of the space available.
If the sequence of formation is shown by horizontal arrangement the
younger formations are placed at the left and the older at the right.
If it is shown by a vertical arrangement the youngest formation is
placed at the top.

Each original map submitted by an author should have at least 4-1/2
inches of blank margin on the right and at the bottom in which to
place the explanation, scale, title, and other matter, but the author
should make no attempt to elaborate these features nor should he
employ a draftsman to letter them carefully. Plainly written ordinary
script is quits sufficient for original maps; the final lettering,
which may consist entirely of impressions from type, will be added
after submittal of a report.


TITLES OF MAPS AND OTHER ILLUSTRATIONS.

The titles of maps should be supplied by authors but are subject to
revision in order to make them agree with established forms. They
should be written in ordinary script, not carefully lettered. They
should state concisely the kind of map, the area shown, the special
features represented, and the county, State, or Territory in which the
area is located. (See p. 58.) Titles are reproduced directly only on
lithographs, three-color prints, photogelatin plates, and other
illustrations that are printed by contractors, not by the Government
Printing Office. The titles of illustrations that are reproduced by
relief processes, such as zinc etching, half tone, and wax engraving,
are printed at the Government Printing Office from type, and proofs
are submitted to the authors for examination.


SYMBOLS USED ON MAPS.

GENERAL FEATURES.

More than 200 symbols have been used on maps to express 25 different
kinds of data, a fact indicating at once a notable lack of uniformity
and a need of standardization. It is of course impossible to provide a
characteristic symbol that can be used uniformly for each kind of
feature, and therefore the same symbol may be used on different maps
to express different things. The symbols shown in Plate II are those
most used on geologic maps. The symbols for dip and strike, fault
lines, mine shafts, prospects, and several others are generally well
known, but on some maps it may be necessary to modify a standard
symbol to express additional distinctions. The symbols shown, however,
will cover all the ordinary requirements of miscellaneous mapping.
Though the plate shows more than one symbol for some features the
symbol most commonly used is given first and should be preferred. The
center of each symbol should mark the location of the feature
symbolized. Symbols are not always platted with sufficient care. On
small-scale maps they are difficult to locate and unless great care is
taken in platting them they are likely to be several miles out of
place. All symbols should be located precisely where they belong.

The symbol showing dip and strike should be accurately platted by
means of a protractor, so that the strike will be shown graphically,
without a number and a degree mark, and not need replatting by a
draftsman or engraver. The dip, however, should be indicated by a
number and a degree mark.

LETTER SYMBOLS.

The letter symbols used on most geologic maps to indicate the ages
and names of the formations represented consist of two or more
letters--an initial capital letter for the name of the system and
one or more lower-case letters for the name of the formation or of
the material, as Qt (Quaternary--lower terrace deposits); Cpv
(Carboniferous--Pottsville formation); COk (Cambrian-Ordovician--Knox
dolomite), etc. The standard usage for this feature is shown in the
geologic folios but is subject to modification in other publications.

In preparing an original geologic map a letter symbol, such as has
been just described, or a number should be put in the proper place in
the explanation, and the same symbol or number should be repeated at
one or more places on the map within the areas to which it refers.
Each area that is indicated by a color should be marked with the
proper symbol in order to make its identification sure, for light
colors especially are likely to fade and mixed colors can not be
discriminated with certainty.

[Illustration: U. S. GEOLOGICAL SURVEY

PREPARATION OF ILLUSTRATIONS PLATE II


SYMBOLS USED ON GEOLOGIC MAPS, ECONOMIC MAPS AND MINE PLANS]

OIL AND GAS SYMBOLS.

A complete set of symbols for maps showing oil and gas is given on
Plate II. Referring to these symbols the chief geologist, in a
memorandum to the Director, writes:

     The symbols used by the Survey in its oil and gas maps have
     not been in accord with those used by the oil companies, nor
     have they been wholly logical. It appears that though they
     were submitted for recommendation they never have been
     formally approved.

     Herewith I submit a code prepared by the geologists of the
     oil and gas section. They conform largely to commercial use
     and embrace its best features as well as the best and most
     logical features of our previous usage, the departures from
     which are, after all, of minor consequence.

     The symbols here submitted [see PI. II] with recommendation
     for approval are founded on a building-up system, so that the
     history and the results of drilling at any location can be
     recorded by slight additions to symbol and without erasure.
     Thus maps may be revised without scratching.

     In drawing these symbols the draftsman should make the rays
     of the gas well distinct and in adding the vertical bar or
     line showing that a hole is dry or abandoned should make it
     long enough to be distinct. It would be preferable to draw
     this bar obliquely, but an oblique position would coincide
     with some of the patterns on certain maps, and it should
     therefore be placed vertically. The vertical line indicates
     the failure or abandonment of the well, the symbol for which
     Is thus scratched off or canceled by the line drawn through
     it. The symbols agree so far with commercial usage that oil
     men will have little need to consult the explanation.

SYMBOLS FOR USE ON MAPS SHOWING FEATURES OF GROUND WATER.

The symbols used on maps relating to ground water represent the
features named below, each of which has been shown in publications
already issued.

  Area of absorption or outcrop.        Area that discharges ground water.
  Depth to water table.                 Quality of ground water.
  Contours of water table.              Area irrigated with ground water.
  Fluctuation of water table.           Nonflowing well.
  Depth to water-bearing formation.     Flowing well.
  Structure contours of water-bearing   Unsuccessful or dry well,
    formation.                          Well with pumping plant.
  Area of artesian flow.                Spring.
  Head of artesian water.

The lack of uniformity in the symbols commonly employed to represent
these features is due to differences in the number of color on the
maps and differences in the scale. Standard colors for the larger
features, such as those for areas of artesian flow, areas of
absorption, and curves showing depths to water table or to
water-bearing formations, can not be fixed, because of considerations
of economy in printing. For example, if light green is the standard
color to be used for delineating areas irrigated by ground water and
no green is used on other parts of the map its use would represent an
additional or special printing, whereas a tint of blue, brown, or
purple, if any of these colors is used for other features on the map,
might be used also for this feature without additional printing.
Therefore the general use of any particular color for a water feature
seems to be impracticable; but this fact should not preclude the
adoption of color standards for use subject to the requirements of
economy in publication.

The ordinary symbols for wells are the open circle and the solid
circle, or dot. Only in the secondary or specific well symbols does
there appear to be lack of uniformity, the choice of secondary symbols
being governed either by personal preference or by the requirements
for specific distinction.

All symbols should, if possible, suggest the things they represent.
Wells are circular and hence the open circle is most used and most
appropriate for nonflowing wells. To indicate a flowing well the
circle is made solid, denoting that the well is full of water. For an
unsuccessful well the most suggestive symbol would be an open circle
with a line drawn through it to denote cancellation. It has been
suggested that if water features, including wells, are to be printed
in blue, unsuccessful wells, or dry holes, be printed in black. A
large circle drawn around the symbol for a flowing or nonflowing well
will appropriately denote a pumping plant at the well.

The accepted symbol for a spring is a dot with a waved tail
representing the direction of flow, if known. This symbol can not be
modified without destroying its prime characteristics, but it may be
accompanied by a letter indicating the kind of spring. An open circle
with a tail might be used on large-scale maps, but it would be out of
scale on other maps, whereas the black or blue dot and tail will fit
maps of any scale.

The following colors and symbols can most appropriately be used to
represent ground-water features. The well and spring symbols can be
varied by adding letters if they are necessary to express other data
than those indicated in the list below.

_General ground-water features._

  Area of absorption or outcrop: Flat color used on the map to
     show the geologic system in which the absorbing formation
     occurs.

  Areas showing depths to water table: Shades of purple and gray;
     if possible the shades showing the areas of least depth
     should be darkest and the shades should grade from those to
     lighter tints.

  Contours of water table, or contours on water-bearing
     formations: Gray or purple curves or lines.

  Areas of artesian flow: Blue flat tint, or fine ruling in blue.
     Depth to water-bearing formations: Gradation of a single
     color or of two related colors from dark for shallow depths
     to light for greater depths.

  Nonflowing artesian areas (pumped wells): Green flat tint, or
     fine ruling in green. Depth to water-bearing formations shown
     by gradation of tint if possible from dark for shallow depths
     to light for greater depths.

  Head of artesian water: Blue curves or lines.

  Areas that discharge ground water: Blue flat tint, or fine
     ruling in blue.

  Areas irrigated with ground water: Green flat tint, or fine
     ruling in green.

  [Illustration] Well, character not indicated. [Illustration]
     Well, nonflowing. [Illustration] Well, flowing.
     [Illustration] Well, unsuccessful or dry. [Illustration]
     Well, nonflowing, with pumping plant [Illustration] Well,
     flowing, with pumping plant. [Illustration] Springs.
     [Illustration] Spring, thermal. [Illustration] Spring,
     mineral.

The standard color scheme should be used if no conditions preclude its
use, but if other colors can be used with greater economy without
sacrificing clearness the use of the standard colors should be waived.


BLACK-LINE CONVENTIONS.

A complete set of the black-line patterns used to distinguish areas on
a map is given in Plate VIII (p. 60), and their application to a
finished drawing is shown in figure 9 (p. 62). These patterns,
however, should preferably not be used by the author in his
preliminary work on an illustration. For this purpose water colors or
colored crayons are preferable, and the distinctions between areas may
be emphasized by letter symbols.


MATERIALS USED IN PREPARING MAPS.

PAPER.

For large and important maps which may at some time be extended to
cover a greater area or which may be made to fit maps already prepared
or published the paper used should be mounted on muslin to reduce to a
minimum the shrinking or stretching caused by atmospheric changes.
Pure white paper produces a better negative than a cream or yellowish
paper and will retain its color longer, but all papers become more
yellow with age and exposure to light.

The following brands of paper are used in the Survey in the
preparation of maps:

"Normal" K. & E., unmounted. Has an excellent surface and comes in
flat sheets, 19 by 24, 22 by 30, and 27 by 40 inches.

"Paragon" K. & E., mounted on muslin. In 10-yard rolls 72 inches wide.
Used in the Survey for large office drawings and maps of large scale.

"Anvil" K. & E., mounted on muslin. In 10-yard rolls 42, 62, and 72
inches wide. Used in the Survey for large drawings.

"Whatman's hot pressed," unmounted or mounted on muslin. In sheets
ranging in size from 13 by 17 to 31 by 53 inches. An excellent paper
for maps. The muslin-backed paper is recommended for use in preparing
large detailed maps and base maps that are to be retained as permanent
records. The muslin provides a durable and flexible backing that
permits the map to be rolled, and paper thus mounted is particularly
serviceable for a map which may be subjected to considerable revision
and to which must be added finally a title, explanation, and other
marginal matter.

"Ross's relief hand-stipple drawing paper." A stiff enameled or
chalk-coated paper whose surface has been compressed into minute
points that stand in slight relief so that a shade made on it with
pencil or crayon is broken up into dots and can be reproduced by
photo-engraving. For use in making shaded drawings, drawings showing
relief by light and shade, etc. Similar paper is prepared for
parallel-line and other pattern effects. In sheets ranging in size
from 11 by 14 to 22 by 28 inches. (See p. 51 for method of using.)

Profile and cross-section paper. In sheets of convenient sizes or in
rolls. Bears lines printed in blue, green, red, or orange, in many
kinds of rulings, which may be selected by reference to catalogues.
Profile and cross-section paper printed in orange is recommended for
preliminary drawings; blue is recommended for drawings that are made
in pencil and submitted for inking in.

BRISTOL BOARD.

For the smaller maps, such as key maps and maps less than 18 by 24
inches, and for small drawings made for direct reproduction,
Reynolds's bristol board is recommended on account of its pure-white
color and its hardness, which permits erasures to be made without
affecting redrawing over the corrected area. It is obtained in 2-ply,
3-ply, and 4-ply sheets. The 2-ply and 3-ply are especially useful in
making delicate brush and pencil drawings and pen and ink drawings.
The sizes used in the Survey are 16-1/2 by 20-3/4, 18-1/4 by 22-3/8,
and 21-1/2 by 28-3/4 inches.

TRACING LINEN.

Tracing cloth or linen is especially useful for large work that will
require considerable reduction. (See p. 18.) Its advantages are that a
tracing that has been carefully made on it over any kind of copy for
direct reproduction by a photo-engraving process can be used for
making a paper negative for contact printing or blue printing. On the
other hand, it is susceptible to atmospheric changes that affect
scale, and the lines traced on it are not reproduced as sharply as
those made on paper. It can be obtained in rolls 30 to 54 inches wide.

Erasures should be made on tracing linen with a hard rubber eraser,
not with a sand rubber or a steel eraser.

INKS.

The best drawing inks are in liquid form, ready for use. They should
be waterproof and equal to the grade known as Higgins's waterproof
ink. When a suitable waterproof blue ink can not be obtained, a good
blue for features of drainage can be made by dissolving a half pan of
Winsor & Newton's prussian blue in water. No good waterproof burnt
sienna ink seems to be obtainable, but a good substitute can be made
by dissolving Winsor & Newton's water color of that name.

Ink lines should be drawn in full strength of color--lines that should
be black must not appear grayish, for example--and pens should be kept
clean. The same pen should not be used for applying two inks, as the
mixture thus produced is likely to thicken or coagulate on the pen. A
little black should be added to colored inks that are used in making
drawings to be reproduced in colors in order to strengthen the lines
for photographic reproduction.

DRAWING PENS.

The pens made by Keuffel & Esser, especially their No. 3202, and
Gillott's Nos. 291, 290, 170, and 303 give complete satisfaction. The
Gillott numbers are given in the order of fineness of the points. No.
291 being the finest. The best cleaner for a drawing pen is a piece of
chamois skin.

PENCILS.

Pencils used for drawing should have leads of a quality equal to those
of the Koh-i-noor brand, in which the grades of hardness are indicated
by 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, 6H, 7H, 8H, and 9H; the
softest grade is 3B and the hardest 9H. The grades most generally used
are B, HB, F, 4H, and 6H.

RUBBER ERASERS AND CLEANERS.

Two kinds of rubber erasers are usually employed in making erasures on
drawings--a hard, dense rubber like the "Ruby," and a soft, pliable
rubber like the "Venus" or "H" (Hardtmuth). The soft rubber is also
useful for cleaning large surfaces. Art gum is also recommended for
this purpose and has the advantage of not disturbing the surface of
the paper.

COLORED PENCILS AND CRAYONS.

Colored pencils and crayons are useful only for coloring preliminary
maps. They are not recommended for use on maps that are to be kept for
reference or to be submitted for reproduction, because the colors rub
off, but they can be used on photographic prints of base maps or on
transparent oversheets, for which the unglazed side of tracing cloth
is well suited. When they are so used register marks should be added
at numerous points on the map and the oversheet, including the four
comers, the color boundaries should be drawn or traced, and finally
the colors should be added. Two or more colors should not be used on
any one area to modify a tone, but each area should be colored with a
separate crayon. Patterns or designs should not be used except to
strengthen contrasts, and for that purpose a pattern may be drawn with
a black pencil over a color.

WATER COLORS.

By dilution to half strength some of the standard water colors will
yield a tint or hue that will contrast with other tints or hues
produced in the same way quits as well as undiluted or full colors
will contrast with one another. The colors named below, except
chrome-yellow and emerald-green, are among those that when diluted
will afford satisfactory contrasts among themselves and with their
full colors and are recommended for use in coloring original maps.

Mauve.              Hooker's green No. 2.
Crimson lake.       Emerald-green.
Orange-vermilion.   Payne's gray.
Burnt sienna.       Lampblack.
Cadmium-yellow.     Sepia.
Chrome-yellow.      Cerulean blue.
Olive-green.

Other pigments spread better than cerulean blue and emerald-green, but
the exceptional purity of color of these two seems to warrant their
use.

JAPANESE TRANSPARENT WATER COLORS.

Japanese transparent water colors, so called, are used by some
geologists. They spread evenly and are convenient for field use, but
they can not be washed out like other water colors, so that when they
are once applied to an area and a change of color becomes necessary
they must be bleached out. A good bleach is sodium hypochlorite, which
should be applied with a brush until the color disappears, and the
area dried with a blotter before recoloring. Light tints of these
colors are believed to be somewhat fugitive if exposed to strong
light.

COLORING GEOLOGIC MAPS.

The colors used on most original maps are not pleasing, a fact that is
of no particular importance, but--and this is of importance--they
often fail to give clear distinctions; the separate areas can not
always be identified or distinguished with certainty. Again, some
colors are fugitive, and when laid on in light tints they disappear
entirely or become uncertain. Much of the difficulty in identifying
and discriminating colors on an author's original maps is due to the
promiscuous mixing of colors. Many persons can not match or
discriminate mixed or broken colors. Hence if the supply of a color
produced by mixing becomes exhausted and the attempt is made to
duplicate it by a second mixture the two will probably fail to match.
It is therefore suggested that colors in full strength and colors
diluted to half strength be used instead of mixtures of two or more
pigments, so that one color in two strengths or tones can be employed
to indicate areas that are to be distinguished. The colors listed on
page 26 will give 24 satisfactory distinctions and will thus supply
all demands for map coloring.

To insure satisfactory contrasts between colored areas on a map,
unlike colors should be placed next to each other--that is, colors
should be placed together that are widely separated in the spectrum,
such as yellow and mauve, red and green, blue and orange, burnt sienna
and olive-green; not such as red and orange, blue and purple, orange
and yellow, sepia and burnt sienna.

A sufficient quantity of water and color pigment to be used for one
formation area on a map should be stirred in a saucer until the
desired tint is produced before it is applied. To maintain the same
tone properly the color should be well stirred every time the brush is
filled; if it is not stirred the brush will on the next dipping take
up a lighter tint, because most pigments, especially those derived
from minerals, tend to precipitate. When the colors are applied the
map should preferably be placed in a slightly inclined position, and
the coloring should be started at the upper boundaries of an area to
be colored, the well-filled brush being pulled toward the painter and
Worked rapidly back and forth horizontally, the edges of the fresh
color being kept wet. If the edges are allowed to dry, a hard line and
a smeared or uneven effect will be produced.

A strong color should generally be used for small areas unless the map
shows also large areas that must have the same color; lighter hues
should be used for large areas. Bright colors are best suited for
areas of igneous rocks, dikes, and veins, and these may be reduced in
strength for the larger areas.

The Survey's color scheme (see p. 63) need not be applied at this
stage of preparation, except in the most general way. Appropriate
final colors can be best selected when the new map is made ready for
engraving. In the author's original maps adequate color distinctions
between areas are more important than the use of standard geologic
colors. Patterns should not be ruled in one color on an original map
to indicate distinctions between different formations of the same age
or period, because such patterns are difficult to produce by hand with
proper uniformity except by engraving.

It is of vital importance that an original base map should be free
from colors and from technical symbols in order that it may be kept
clean for photographing and preserved for possible future use. Such a
map should preferably be photographed in order to obtain prints on
which to add the colors and symbols; the use of an oversheet for this
purpose is not nearly so satisfactory. When photographed a base map
should be reduced to publication scale in order to save the additional
cost of a larger negative, and this reduced map may be made up for
publication by the addition of colors and symbols, title, explanation,
etc.; but the lithographer will also need the original base map from
which to make his reproduction.


DIAGRAMS.

ESSENTIAL FEATURES.

The term "diagrams," as used here, includes such illustrations as mine
plans, profiles, sections, stereograms, and maps that are more
diagrammatic than cartographic. The first essential in the original
drawings for simple diagrams is clearness of copy. Simplicity of
subject does not warrant hasty preparation, for an original sketch
that has been carelessly drawn and is inaccurate or inconsistent in
detail may lead to serious errors. Ruled paper printed especially for
platting profiles and cross sections should be used. Curves or graphs
made by an author with pencil on blue-lined section paper may be inked
by more skillful draftsmen. An author's pencil sketches are usually
satisfactory if they indicate plainly the facts to be represented, but
they should be prepared with some care as to detail. Tables and like
matter are not generally satisfactory material from which to prepare
drawings. In drawings for diagrams that are to be printed in the text
as figures the use of large, solid black bars or of conspicuous areas
of solid black is objectionable, because the black is likely to print
gray and to appear uneven in tone. Ruled tints or cross lining give
better effects. Stereograms should be prepared by an author with
especial care, for they represent facts only as the author sees them,
and the author's view must be imparted to the draftsman graphically.
The "third dimension"--the relief--in such drawings is not easily
expressed and should be brought out clearly in the author's rough
sketches.

For illustrations of apparatus photographs are preferred, but if rough
sketches are submitted they should show not only correct relations but
all dimensions.

PLANS OF MINE WORKINGS.

Blue prints obtained from mining companies are acceptable for plans of
mines or underground workings, but all unnecessary or irrelevant
details on such plans must be canceled and all essential features
retained, and every essential feature, especially any added data, must
be clearly interpretable. Many such blue prints are so large and
unwieldy that they must be greatly reduced by photography before they
can be redrawn. If the lines are too weak to photograph, a tracing of
the essential parts can be made and reduced to about twice publication
size. The shadowless drafting table, described on pages 47-48, is well
adapted to the work of making such tracings. Blue prints can also be
pantographed to any convenient size if the details are not too minute
or complex.

[Illustration: Figure 2.--Conventional lines used in preparing plans
and diagrams of mine workings to distinguish different levels.]

The levels in plans of underground workings can be differentiated in
finished drawings by a system of conventional outlines in black, as
shown in figure 2, by conventional patterns or symbols within plain
outlines, or by colors. Such plans should not be printed in colors
unless the maze of workings is so complex that lines showing the
different levels would become confused or obscure if printed in black.

SECTIONS.

The standard forms of geologic sections are shown in the geologic
folios. Structure sections should be prepared with great care as to
detail but without attempt at refinement of lines and lettering. The
author's drawing of a section along a line or zone that is not
definitely indicated by a line on an accompanying map should be so
prepared that it may be copied exactly. On the other hand, the
draftsman, in reproducing a section that represents the structure
along a given line or zone, may be able to make the outcrops coincide
with the topography and the formation boundaries shown on the map, but
the structure, or the interpretation of it to be given, should be
carefully worked out by the author. All essential facts relating to
bedding, folding, faulting, crosscutting dikes and veins, or other
significant details should be indicated with precision. No attempt
need be made to draw firm, steady lines so long as the essential facts
are clearly expressed.

All sections should be drawn to scale, and both the vertical and the
horizontal scale should be given on the drawing. These scales should
be uniform if possible, or at least the vertical exaggeration should
be minimized. Too great vertical exaggeration creates distortion and
is grossly misleading. Sections should be drawn to scale on ruled
paper prepared for the use of authors. Such paper may be obtained on
requisition.

[Illustration: Figure 3.--Section and perspective view showing
relations of surface features to the different kinds of rock and the
structure of the beds.]

A kind of cross section which is not often used but which gives a
more pictorial and clearer conception of underground relations than
other kinds is made by adding a sketch of the topography above the
section. This sketch should be a perspective view, in which the
prominent features shown hypothetically in the section below it will
be reflected in the topography. Such a sketch might show, for example,
not only monoclinal slopes, "hogbacks" due to steeply upturned beds,
terraces, escarpments, and like features, but volcanic necks or other
extruded masses in their true relations to the underground geology of
the country. (See fig, 3.) In submitting the draft of such an
illustration the author should, if possible, submit also a sketch or
photographs of the adjacent country and indicate on the section the
point of view by notes such as "Sketch A made at this point," "See
photograph B." The sketch will be more useful if it is prepared on a
scale consistent with the details of the section. It may be made with
a pencil and should show as well as possible the relations of the
features in the landscape to those in the section. Some good examples
of illustrations of this type can be found in Powell's "Exploration of
the Colorado River," pages 182-193. One simpler figure of the same
kind is given on the cover of the geologic folios.

In preparing original drawings representing columnar sections, or
sections in wells or ravines, the author should indicate all
well-defined or important local features of structure, such as
cross-bedding, ore bodies, or lenses. If there are no unusual features
or details, the subdivisions need be identified only by names of
materials, such as "thin-bedded limestone," or "slates with some
coal," the coal beds being shown. The sections should, however, be so
plotted and subdivided by the author that each section or group of
sections will be complete in its crude form. The compilation of
various parts into one unit and the construction of columnar sections
by reference to tables alone is an essential part of the author's
original preparation.

[Illustration: Figure 4.--Sections of coal beds. The Figure shows the
publications size and the arrangement at the sections. Each section
should be drawn three-tenths or four-tenths of an inch wide and
reduced one-half. Thicknesses can be indicated by numbers, as shown on
sections 1 and 10, or by bar scale.]

Sections designed to show the relative thickness of beds of coal,
arranged in groups for publication either as plates or figures, should
be drawn in columns three or four tenths of an inch wide and reduced
one-half, as shown in figure 4. These sections, whether correlated or
not, should be drawn to some definite vertical scale and should show
the thickness of the coal beds, preferably by numbers indicating feet
and inches, the other material being symbolized and the symbols
explained graphically, as shown in figure 4. The vertical scale should
always be stated for the use of the draftsman. A bar scale may be
used instead of figures showing the dimensions of the individual beds.

LITHOLOGIC SYMBOLS.

The symbols used to indicate the various kinds of rocks illustrated in
sections and diagrams are shown in Plate III. The units or elements of
these symbols may be spaced more openly in generalized diagrammatic
sections than in sections that show great detail.

Symbols should be used consistently throughout a report, and in order
to make them consistent a set showing the symbol to be used for each
kind of rock to be indicated should be prepared before the original
drawings are made. Some inconsistencies may be unavoidable on account
of the small size of some areas shown and the contrast needed between
others; but the deviations from the set of symbols adopted should be
minimized.


USE OF PHOTOGRAPHS AS ILLUSTRATIONS.

ESSENTIAL FEATURES.

The foundation of a good photographic print is a good negative, and
the best prints for reproduction as illustrations are those made from
negatives in which the illumination is evenly distributed and the
details are sharp--such negatives as are obtainable only by the use of
small stops and correct focusing. A good print should not present too
sharp contrasts between its dark and its light parts; if it does, the
printed reproduction will show a loss of detail in both. Sufficiency
of detail depends largely on focus, stopping down, and timing;
brilliancy is the direct result of ample illumination by sun or
artificial light, without which a photograph will be dull or "flat"
and generally unsatisfactory for reproduction. Bad weather may prevent
good field exposures, yet even in bad weather acceptable negatives may
be obtained by judicious focusing, stopping down, and timing. If a
negative is overexposed it may be full of detail, but flat and too
thin to print well. If underexposed it will show no details in its
lighter parts and the shadows will be black; and a black shadow is
nothing less than a blemish. Some detail should appear in all shadows
and in the middle tones, and some should appear in the high lights;
and a print in which these are evenly developed and in which the
illumination is distributed uniformly is technically perfect.

Unfortunately not all field photographs are good, so an author must
select from his collection those which will make the best half tones.
In making this selection he should of course consider, first, the
scientific value of the photograph, and next, its pictorial or
artistic quality, which, though of secondary importance, should
nevertheless be kept in mind. A feature worthy of illustration
deserves good pictorial expression; if it is of superior scientific
interest it should not be represented by an inferior photograph.
Fortunately, a good, accurate drawing may be made from a poor
photograph, and a photographic view that has only minor defects can be
successfully retouched. Photographs that need much retouching should
generally be larger than publication size, for the effects of
retouching--brush marks, etc.--will be softened by reduction.
Photographs that need only slight retouching need not be larger than
publication size. A photograph can rarely be satisfactorily enlarged
in reproduction unless it is sharp in detail and requires no
retouching.

[Illustration: U. S. GEOLOGICAL SURVEY

PREPARATION OF ILLUSTRATIONS. PLATE III.

LITHOLOGIC SYMBOLS USED IN STRUCTURE AND COLUMNAR SECTIONS TO
REPRESENT DIFFERENT KINDS OF ROCK]

Unmounted prints are always preferable for use in making
illustrations. A group that is to form a single plate should be placed
in an envelope bearing the number of the plate and its title, and each
print of the group should bear a corresponding number, written in
pencil on its back. The envelope will protect the prints and keep them
together, and the numbers will identify them. Red ink should not be
used to mark photographs, as it is likely to penetrate the coating or
even the fiber of the paper, so that it can not be erased.

If a print is of doubtful quality two copies of it should be
submitted--one glazed, the other having a dead finish or "mat"
surface, which is generally preferable if the print must be
considerably retouched. The best prints for use as illustrations are
those made on "regular" or "special" semimat velox and glossy haloid
papers. The author should indicate prints that may be grouped together
according to their relation geographically or by subject. Generally
two half tones will be combined on a page, and the list of
illustrations should be prepared accordingly.

With slight trimming and reduction, three photographs measuring 3-1/4
by 5-1/2 inches may be made up one above the other to form a full-page
octavo plate. Four photographs in which the longer dimensions
represent vertical distances may sometimes be used if they are placed
sidewise on the page, with side titles.

Some photographs may be reduced to the width of a page by trimming
instead of by photographic reduction, which may involve loss of
detail. The author should clearly indicate the extent of such trimming
as they may bear without loss of essential details. The trimming is
best done during the final preparation. A line should not be drawn
across a photograph to mark such trimming, but the position of the
line or lines should be indicated either on temporary mounts, on the
backs of the prints, or by a statement, such as "One inch may be cut
off on right, one-fourth inch on left, and one-half inch at bottom."

COPYRIGHTED PHOTOGRAPHS.

Section 4965 (ch. 3, title 60) of the Revised Statutes, amended by act
of March 2, 1895 (Stat. L., vol. 28, p. 965), provides that no
copyrighted photograph may be used without the consent of the
proprietor of the copyright in writing signed in the presence of two
witnesses. A penalty of $1 is imposed for every sheet on which such a
photograph is reproduced without consents, "either printing, printed,
copied, published, imported, or exposed for sale." An author should
therefore obtain the written consent of the owner of a copyrighted
photograph to use it, and the letter giving this consent should be
submitted with the illustration.

SOURCES OF PHOTOGRAPHS.

Every photograph submitted with a manuscript should bear a memorandum
giving the name of the photographer or the owner of the negative. If
the negative is in the Survey's collection that fact should be stated,
as "Neg. Keith 318." The Survey receives many requests for copies of
photographs that have been reproduced as illustrations in its
publications, and replies to these requests will be facilitated if the
Survey's number or the source of each photograph presented for use as
an illustration is stated as above on the photograph.


LENDING ORIGINAL PHOTOGRAPHS AND DRAWINGS.

A photograph that has been used in making a half-tone cut for a Survey
report can not be lent, but if the negative is on file a print can be
furnished at cost; and a Survey drawing that is well preserved can be
photographed and a print furnished, also at cost. Requests for such
prints should be addressed to the Director.

UNPUBLISHED PHOTOGRAPHS.

The Survey can not issue a copy of an unpublished photograph except
upon the written approval or requisition of the person under whose
name the negative is filed. This requirement does not apply to a print
needed for official use, nor to a print made from an old negative
reserved under the name of any present member of the Survey or from a
negative that has been released by the person under whose name it is
filed.

Authors using Survey photographs in unofficial publications are
requested to acknowledge the source of the photograph by adding to the
printed title such a statement as "Photograph by U. S. Geological
Survey (David Whits)."


SPECIMENS.

GENERAL REQUIREMENTS.

Specimens other than fossils that are to be illustrated in a report
should be photographed before they are submitted, but the requisition
for the photographs should be initialed by the chief illustrator, who
will indicate the kinds of prints needed. Duplicate photographs of the
specimens should be made up into temporary plates by the author and
submitted with his other illustrations, the specimens being retained
subject to call, if needed, when the illustrations are finally
prepared. Should a colored illustration of a specimen be needed,
however, the specimen must be submitted with the report, and a
different kind of print, preferably one made on platinum or other
special paper, will be obtained by the section of illustrations.

BORROWED AND FRAGILE SPECIMENS.

In submitting specimens to be illustrated an author should call
attention to those that have been borrowed and to those that are
fragile. Borrowed specimens will receive first attention, so that they
may be returned promptly.

TRANSMITTAL OF PALEONTOLOGIC SPECIMENS.

All requests for paleontologic illustrations should be addressed to
the Director. The letter of transmittal should state the title of the
paper, the form of publication desired (bulletin, professional paper,
or monograph), and the status of the manuscript, whether completed or
in preparation. If the paper is unfinished an estimate of the number
of illustrations required should be given, and the special reasons for
prompt preparation should be fully stated. A letter transmitting a
second or third lot of fossils should refer to the preceding lot or
lots if all the fossils are to be used in illustrating the same paper.

Fossils that are to be drawn should be sent directly to the section
of illustrations, but those that are to be photographed and require
unusual posing or that are extremely delicate and valuable may be sent
directly to the photographic laboratory to avoid repeated handling.
Each specimen or, if it is very small, each box or bottle containing a
specimen should be numbered, and each lot should be accompanied by a
list giving their names and numbers. Full instructions as to size of
reproduction, together with sketches showing the point of view
preferred and any special features to be displayed should also be
submitted. All specimens that show strong colors and all groups of
specimens that are not uniform in color will be coated by holding them
in the vapor of ammonium chloride unless directions to the contrary
are given by the author of the paper. As it may not be desirable to
apply this process to soft or fragile specimens or to specimens that
have been borrowed an author should indicate any specimens that may
not be so treated. Specimens whose color aids in revealing detail are
not so coated. If any features of a specimen are unusual that fact
should be stated so that the photographer and the retoucher may
perform their work according to the requirements.

MAKING UP PLATES.

Two or more illustrations may be combined to form one plate in order
to permit easy and close comparison as well as for economy, for if a
particular illustration is too small to make a full plate and is not
suitable for enlargement other illustrations that are closely related
to it may be put on the same plate. The size of the printed page as
given in the table on page 11 will determine the size of the plate.

In making up plates composed of a number of figures the author should
endeavor to group related figures together and at the same time to
observe proper regard for artistic effect, but as figures vary in size
and shape a grouping according to relations may not be possible in
some plates. If related figures can not be kept together the larger
and darker figures should be placed in the lower part of the plate and
the smaller and lighter above. If a plate consists of one large figure
and several smaller ones the large figure should be placed below and
the smaller figures above.

A number designating a figure should be placed immediately below the
figure, and a series of such numbers should preferably begin with 1 in
the upper left corner and continue consecutively across and down
through the plate. This arrangement is not always possible, however,
on account of variations in the size of figures.

As drawings of fossils or other specimens are prepared separately and
grouped into plates, and as most paleontologists make up their own
plates, each in his own way, there is naturally great dissimilarity in
methods and in results. Ordinary white or light-gray cardboard should
be used, and the figures that are to make up a plate should be
arranged as stated above but not securely pasted until the grouping is
satisfactory. In trimming each drawing or photograph the author should
be careful to leave room at its lower edge for the number. Small
drawings or photographs, such as paleontologists use, when pasted on
bristol board or other board faced with tough paper are difficult or
impossible to remove without injury if they have to be remounted;
figures pasted on ordinary white or gray cardboard can be removed
without difficulty. Each plate should be made up in a size to fit the
volume or in its correct proportion to a page in the volume in which
it is to be used (see table on p. 11), and each figure should be
properly oriented--that is, all vertical lines, or the vertical axis
of each specimen, should be parallel with the sides of the plate. When
the figures are being mounted care should be taken that the mucilage
or paste does not exude under pressure and cover any part of the
drawing or photograph. The same attention should be given to pasting
on numbers. Inattention to these details may produce results that
will affect the reproduction of the plates.

Ordinary mucilage may be used for mounting drawings and photographs,
but photo paste gives good results and is perhaps cleaner to handle.
Dry-mounting tissue is well adapted to mounting single illustrations
but not groups of figures. Liquid rubber is sometimes used, but it is
not suitable for mounting small figures, such as drawings and
photographs of fossils. It can be used satisfactorily for mounting
temporary plates and for mounting photographs in albums and on large
cards for study or exhibition; but it has not proved to be a permanent
adhesive. Its special merit is that it does not cause either the
photograph or the mounting sheet to warp. It is applied by spreading
it evenly over the back of the photograph with the fingers. The
superfluous rubber can easily be removed from the hands and from the
cards or sheets when it is dry. Anything mounted with liquid rubber
can be easily removed.

If a plate is to be made up of a small number of figures that require
different reductions, the author, instead of mounting or pasting the
separate figures on one card in the manner already indicated, may draw
a rectangle of the size of the printed plate and sketch within it the
several figures in their respective sizes and positions. These "dummy"
plates or layouts should be numbered as plates, and they may bear
captions and titles. The photographs or drawings represented by the
sketches should then be numbered to identify them with the sketches on
the dummy plate, and those that pertain to each plate should be
inclosed in an envelope attached to the dummy plate. A plate made up
in this manner will meet every requirement of the photo-engraver or
lithographer.

If a paleontologist so desires, his plates can be permanently made up
after he has transmitted his material, but he should always submit a
tentative arrangement.




REUSE OF ILLUSTRATIONS.


If an author desires to use in modified form an illustration already
published, whether by the Geological Survey or by an outside
publisher, he should furnish a print or tracing of the illustration
showing the changes desired. If the illustration is not to be modified
he need only give the title of the volume in which it was used, with
the number of the page, figure, or plate, and he need not make a
sketch of the illustration or furnish a dummy; but its title should be
quoted and proper reference should be given in the list of
illustrations. Due credit should be given to the author or publisher.

The original cuts of illustrations will be kept for one year after the
report for which they were made has been published, and authors of
later reports may and should reuse, whenever practicable, any such
cut that will serve as an illustration. In the author's list of
illustrations such a cut should be referred to by its number as plate
or figure and the volume in which it was first used.

An electrotype of any cut on hand will be furnished for use in
publications other than those of the Geological Survey at the cost of
making, which is 3-1/2 to 5-1/2 cents a square inch of printing
surface. The minimum charge for a single electrotype ranges from 46 to
60 cents.




APPROVAL OF FINISHED ILLUSTRATIONS.


After the drawings for a report have been prepared they will be
submitted to the author or to the chief of his branch or division for
examination. The finished drawings will be accompanied by the
"originals," with which the author should carefully and thoroughly
compare them. After making a thorough comparison he should mark
lightly with a pencil, on the finished drawings, all necessary
corrections, or indicate his approval subject to such corrections and
additions as may be required. He should verify all type matter and
other lettering and assure himself that no mistakes have been made in
grouping the photographs into plates, especially such as have been
regrouped since they left his hands. The author's list of
illustrations will be submitted with the new drawings for this
purpose.




REVISION OF ILLUSTRATIONS.


All illustrations receive editorial revision before they are sent to
the engravers. After they are drawn they are examined with reference
to their scientific features and their accuracy, and then in turn with
reference to the correctness of geologic names and geographic names
and to errors in statement and in spelling. Each illustration thus,
before it is completed, receives critical examination by persons
qualified in particular kinds of work to detect errors or omissions.




SUBMITTAL OF PROOFS.


The first proofs of all illustrations are submitted to an author when
he is within reach, but if he is in the field and the transmittal of
the proofs to him is likely to cause too much delay they are submitted
to the chief of the branch or division in which the report was
prepared. Second proofs of the more complicated illustrations,
particularly geologic maps, may be submitted. An author's examination
should be confined principally to the revision of the scientific
features of his illustrations, but suggestions as to general
effectiveness are always acceptable.

The process to be used in engraving each illustration is stamped in
its lower left corner. In examining proofs an author should note the
following facts:

1. Changes can not be made in zinc etchings except by eliminating
parts, cutting away defects, and connecting lines. If additions are
required reengraving is generally necessary, and reengraving should
preferably be avoided.

2. Changes can be made in half-tone plates only by re-etching certain
parts to make them lighter and by burnishing certain parts to make
them darker. If the proof shows a general loss of detail the fault may
lie either in the proving of the cut or in the reproduction. If it is
in the reproduction it can not be remedied without reengraving. A
slight loss of detail may be expected in all half tones, especially in
those that are smaller than the copy submitted.

3. Minor changes can be made in photolithographs and
chromolithographs, but changes can not be made twice in one place
without danger of affecting the printing. It is customary to approve
all lithographic proofs subject to the corrections indicated, the
printed edition being examined and compared, but if the changes are
numerous and radical second proofs may be required. Second combined
proofs of chromolithographs are very expensive. (See p. 89.)




PROOF READING ILLUSTRATIONS.


An author should examine the proofs of his illustrations closely and
should compare them carefully with the original drawings. A mere
cursory examination may fail to detect errors that have not been
caught by the regular proof reader. Every correction desired should be
clearly indicated with pen and ink in the body of the proof and
inclosed in a loop from which a line should be carried to a marginal
note or comment, but if the time available is short a pencil may be
used. In correcting type matter or lettering (such as that in a
geologic legend or explanation) the ordinary proof reader's marks
should be used. The author or the person examining the proofs should
initial each one at the place indicated by a rubber stamp.

Proofs should be held only long enough to examine them properly and to
compare them with the original illustrations, for a time limit is
fixed in each contract for engraving, and if the author holds proofs
beyond a reasonable time he causes a delay in the fulfillment of the
contract.

As the illustrations for many reports contain important data that will
be discussed in the text, proofs of illustrations can not be supplied
to any applicant without consent from the Director's office.




GENERAL CONSIDERATIONS.


The following requirements are essential to obtain good original
illustrations:

1. The material selected should be pertinent and expressive; it
should have the qualities essential to good illustrations.

2. The character of the report and the size of the illustrations
should be kept clearly in mind. If the report is preliminary or
ephemeral the illustrations should be simple and inexpensive. If the
report represents the sum of knowledge on the subject treated or the
last word on some particular area the illustrations may be more
elaborate. The character of a report generally determines the form of
publication, which, in turn, determines the size of the pages and the
size of the plates and figures. Every sketch made should be larger
than publication size--preferably twice publication size--whether it
is a simple diagram or a base map.

3. The kind of reproduction that is apparently needed should be fully
considered, for it should have some relation to the kind of report.
The illustrations for short-lived reports are reproduced by the
cheaper processes. Those for hurried reports are reproduced by
processes that can be worked quickly, but no process should be
considered that will not give a clear reproduction of essential
details.

4. Clearness of preparation of original matter is invariably
essential. An author should not expect the draftsmen or the editors to
supply missing links. Each original should be complete and should be
so made that it can be understood and followed without question.
Changes made in the finished drawings or on proof sheets are expensive
and delay publication.


PART II. PREPARATION BY DRAFTSMEN.




GENERAL DIRECTIONS.


The work of preparing illustrations such as are used in the reports of
the Geological Survey is essentially that of making finished drawings
from more or less crude and imperfect material furnished by authors to
illustrate certain features or phenomena discussed in their
manuscripts. Each finished drawing must be so prepared that it can be
reproduced in multiple by one of several processes of engraving. The
author's sketches and other material are commonly called "originals";
the finished illustrations are known by the engravers as "copy."
Though most engraver's copy consists of more or less elaborate
drawings that are to be reproduced in facsimile by "direct" processes
without the interposition of handwork, some of it consists of more
roughly prepared copy which is accurate in statement but requires
complete manual or "indirect" reproduction. The direct processes in
use are zinc etching, half-tone engraving, photolithography,
three-color half tone, photogravure, and photogelatin. The manual or
indirect processes are wax engraving, wood engraving, engraving on
copper and on stone, plain lithography, and chromolithography. These
processes are described on pages 72-90.

Part I of this pamphlet contains some matter that is pertinent to
final preparation and should be consulted by draftsmen.

To prepare a drawing that will be in every way suitable for
reproduction usually requires experience of a kind not acquired in
many other kinds of drafting, such as preparing engineers' or
architects' drawings, because the drawings themselves or blue prints
made directly from them are the things the engineer or the architect
desires. Drawings prepared for reproduction are generally made larger
than publication size, and it is therefore necessary to gage each
line, letter, or feature for a definite reduction. Engineers' and
architects' drawings generally do not require preparation for
reproduction by any process, but in preparing illustrations for the
reports of the Geological Survey reproduction must be fully considered
at every step, and each drawing must be made according to the
requirements of a certain selected process and gaged for a certain
reduction. The draftsman should therefore know how to plan each
drawing step by step for an engraved cut, a lithograph, a text figure,
or a plate, always with a definite result in view. He should be
familiar with processes of engraving and should know the special
requirements of each process, and he should be able to prepare
drawings for any specified reduction in a way to insure good, legible
reproduction.

The geologic draftsman should read and study such textbooks of geology
as those of Dana and Geikie and should familiarize himself with
structural geology, the geologic time divisions, and geologic
nomenclature. He should be able to prepare a simple, effective
illustration from complicated rough originals and to supply minor
missing essential parts or features. To perform his work successfully
he must possess mechanical skill and some artistic taste, as well as
good eyesight and great patience.




INSTRUMENTS.


The following list of draftsmen's instruments is practically complete.
Those which are considered indispensable are marked by asterisks; the
others may be used according to individual preference. The same kind
of instrument may be duplicated in different sizes according to the
variation in the demands of the work.

   Air brush and connections.          Pens, Payzant's, 1 set.
   Beam compass.                      *Pencils, best quality, graded
   Bow pen, drop spring.                leads.
  *Bow pen, steel spring.             *Protractor.
   Bow pencil, steel spring.           Railroad curves, pearwood, 1 set.
  *Brushes, red sable.                 Railroad pen.
   China saucers.                     *Railroad pencil.
  *Color box.                          Reading glass.
  *Compass, pen and pencil points.    *Reducing glass.
   Crayons, assorted colors.          *Ruling pen.
   Curve rule, adjustable.             Scale, boxwood, 12 inches long,
  *Dividers, plain.                      with divisions of millimeters
  *Dividers, proportional.               and inches.
   Dividers, steel spring.             Scales, boxwood, triangular.
   Drawing boards, several sizes.      Section liner (parallel ruling
   Eraser, glass.                        device).
  *Eraser, rubber, hard.               Straightedge, steel, 24 inches.
  *Eraser, rubber, soft.               Straightedge, steel, 36 inches,
  *Eraser, steel.                        with divisions for hundredths
   Erasing shield.                       of an inch and millimeters.
  *French curves, xylonite.           *Straightedge, wood, 24 inches.
   Microscope, low power and          Swivel or curve pen.
     lenses.                          Thumb tacks.
   Palette knife.                      Tracing point, steel.
   Pantograph.                        *Triangle, 45°.
   Pens, double-pointed.              *Triangle, 60°.
  *Pens, Gillott's, Nos. 170,         *T square, pearwood, xylonite edge.
    290, 291.                         *Tweezers, dentist's.
  Pens, K. & E., drawing. No. 3202.



CLASSIFICATION OF MATERIAL.


The draftsman handling the drawings and other original material
submitted by the author of a report for its illustration should first
group them, as far as possible, into kinds or classes, in order that
he may decide how each illustration should be prepared (1) to express
most effectively the author's purpose, (2) to insure reasonable
economy in preparation and in reproduction, and (3) to meet the
requirements of the processes of reproduction selected. All similar
illustrations for one publication should be prepared in the same
general style. In a series of geologic sections, for example, the same
lithologic symbols should be used throughout for the same kinds of
rocks. The titles, explanations, and captions of the maps should also
agree with one another in general style and in details of workmanship.

The draftsman should determine in advance the reduction for each
drawing or for each group of drawings, in order that he may use the
same size of letters or the same kinds of type for the lettering on a
series of drawings that require the same reduction. The reduction
should preferably be marked in fractions (as "1/2 off," "1/4 off" or
"reduce 1/2," "reduce 1/4"), and the choice of the same reduction for
a group of drawings will not only insure greater uniformity in the
drafting and in the reproduction but will permit the drawings to be
reproduced more economically, for the engraver can photograph them in
groups instead of each one separately.

The draftsman should therefore note and consider (1) the special
features shown in the author's originals; (2) whether or not these
features have been plainly indicated and whether the originals are
complete; (3) the size of the printed page of the volume in which the
illustrations will appear and the reduction required for each drawing;
and (4) the process by which each drawing should be reproduced. If an
original is of doubtful or uncertain interpretation or appears to be
incomplete the draftsman should confer with the author of the paper if
he is within reach or should bring the matter to the attention of the
chief of the branch; otherwise he may waste much time in making the
drawing.




PREPARATION OF MAPS.


PROJECTION.

The base maps furnished by authors (see pp. 13-14) are prepared in
many different ways and in different degrees of refinement and of
crudity, but the work of redrawing them for reproduction involves
well-established and generally uniform principles. All maps except
those of very extensive areas should be based on a map projection
which will show with a minimum of distortion the effect of the
curvature of the earth. The polyconic projection (see fig. 5) is used
for most Government maps. In this projection the central meridian is
a straight vertical line, and each parallel of latitude is developed
independently of the others. The mathematical elements of map
projection are given in tables published by the Geological Survey[6]
and the Coast and Geodetic Survey.[7] Figure 5, however, illustrates
the mechanical or constructional features of the polyconic projection
and if used in connection with the published tables will probably be
a sufficient guide for projecting a map on any desired scale.

[Footnote 6: Gannett, S. S., Geographic tables and formulas, 4th ed.:
U. S. Geol. Survey Bull. 650, 1916. See also Gannett, Henry, Manual of
topographic methods: U. S. Geol. Survey Bull. 307, pp. 85-86, 1906.]

[Footnote 7: Methods and results: Tables for the projection of maps
and polyconic development; Appendix No. 6, Report for 1884; Tables for
a polyconic projection of maps, based upon Clarke's reference spheroid
of 1886; 3d ed., 1910.]

[Illustration: Figure 5.--Diagram illustrating method of projecting a
map.]

In projecting a map first select a convenient measuring scale for
setting off the dimensions given in the tables, or if no scale is at
hand one may be constructed. Measuring scales are made, however,
bearing divisions for miles and kilometers and finer subdivisions of 6
to 100 parts. They include the ratios of 1:31,250, 1:31,680, 1:48,000,
1:62,500, 1:63,360, 1:125,000, 1:250,000, 1:500,000, 1:1,000,000, and
others. On a map drawn on the scale of 1 to 63,360, for example, 1
inch would represent 1 mile; on a map drawn on the scale of 1 to
1,000,000, 1 millimeter would represent 1 kilometer, and so on. It
will be seen that the use of a scale that shows in ratios, such as
those just given, the actual distance on the ground as compared with
the unit representing the same distance on the map will reduce the
possibility of error.

The method of projecting a map, illustrated in the accompanying
diagram (fig. 5), is as follows: First draw a straight vertical line
(A) through the middle of the sheet to represent the central meridian
of the map and a line (B) at the lower end of this line exactly at
right angles to it to represent the bottom of the map. Then set off on
the line showing the central meridian the distances between parallels
given in Table 6 on page 36 of "Geographic tables and formulas" (Bull.
650). It should be noted that the figures in these tables give the
distance, in meters and statute miles, of 1° on a meridian measured
30' each way from a point where the meridian is intersected by a
parallel. The exact distances between parallels as measured on the
ground are given in the Coast and Geodetic Survey tables, or they may
be computed from Table 6 of "Geographic tables and formulas" by adding
the sum of the figures given for any two latitudes 1° apart and
dividing by 2.

The distance between parallels that are 2° apart, as shown in the
diagram, may be computed from Table 6 of "Geographic tables and
formulas," as follows:

                                   Meters.         Meters.

1° of latitude on 37th parallel = 100,975.1 / 2 =  55,487.5
1° of latitude on 36th parallel                 = 110,956.2
1° of latitude on 35th parallel = 110,937.6 / 2 =  55,468.8
                                                  ---------
True distance from 35° to 37° latitude          = 221,912.5

The distances given in the diagram were obtained by adding the figures
given in the Coast and Geodetic Survey tables, which yield the same
results. Other tables in Bulletin 650 give the true distances in
inches on maps of certain standard scales.

Through the points thus obtained on the central meridian draw lines at
right angles to the vertical line. Along these horizontal lines lay
off the dimensions in the column headed X, Table 6 (pp. 39-47) of
"Geographic tables and formulas" as required for each individual
map--in the diagram every alternate degree. Draw vertical lines at
these points and set off the distance Y in the same table in a similar
manner, and the points so found will be the points of intersection of
the respective meridians and parallels. Figures are given on the
diagram for the thirty-fifth parallel only.


DETAILS OF BASE MAPS.

Anyone who attempts to draw a base map must, first of all, know how
each feature or part of the map should be represented. Most of the
conventional symbols for features shown on base maps are well
established and should invariably be used; for instance, a line
composed of alternate long and short dashes (not dashes and dots)
represents a county boundary, and a line or two parallel lines across
which short lines are drawn at regular intervals represents a
railroad. If he finds that two or more symbols have been widely used
to represent the same feature the draftsman should select the one that
is best suited to the map in hand. The correct forms of the
conventional symbols or features to be used in preparing miscellaneous
maps are shown in Plate IV, but the size and weight of each line or
symbol must depend on the size and character of the map.


TRANSFERRING OF COPYING.

TRACING.

The oldest method of transferring a map or parts of a map or other
drawing to another sheet is that of copying it by means of tracing
paper. This method, though still used for simple work, has given way
to quicker and more effective methods. By one of these methods a piece
of thin, fairly smooth paper (not necessarily transparent) is coated
with graphite by rubbing over it a soft pencil. When the graphite has
been evenly distributed over it, this sheet is laid upon the drawing
paper, coated side down, the map or other subject to be copied is laid
upon the graphite-coated sheet, and the two outer sheets--the drawing
paper and the map--are securely fastened together. By a steel tracing
point or very hard pencil the lines and other details of the matter to
be copied are then firmly and carefully traced and thus transferred to
the clean drawing paper beneath.

For maps that show several features in different colors sheets rubbed
with blue, orange, brown, or green pencils may be used, one after
another, for tracing each set of the features. Red should not be used,
as it is not easily erased. This method insures distinctive lines for
the separate features and prevents the confusion that might result
from the use of one color only. Exact register of the features shown
in the several colors used may be insured by fastening one edge of the
drawing to be copied to the drawing paper by mucilage or thumb tacks.
The colored sheets may then be slipped in and out without altering the
position of the lines or symbols for one set of data with relation to
those for the others.

In the final preparation of a base map to be engraved and printed in
colors--for example, black, blue, and brown--tracings of the three
colors appearing on the original base should generally be transferred,
as described above, to one sheet of paper and thus worked up into a
three-colored map. It is usually unnecessary and undesirable to draw
each color on a separate sheet. The preparation of separate drawings
may facilitate reproduction, but if they are made on tracing cloth the
usual uneven shrinking or stretching of the cloth may produce
misregister in the printing; therefore it is safer to make a single
drawing, so that the photolithographer can make three negatives and
separate the colors by painting out or "opaquing" the colors not
wanted on each negative. A map drawn on a single sheet is also less
bulky and can therefore be more conveniently handled and compared with
proof.

If for any reason separate tracings for the different colors to be
used on a map are considered desirable they should be made on linen
cut from one roll and in the same direction according to the warp and
woof.

CELLULOID TRANSFERRING.

In the celluloid method of transferring a map or parts of a map to
paper upon which a complete new map is to be drawn the map or part of
the map to be copied is photographed to the exact scale of the new
drawing and reproduced in graphite on thin sheets of celluloid.

The celluloid sheet is then laid face down in the correct position on
the drawing paper and firmly rubbed on the back with a steel
burnisher, which makes a perfect offset of the map on the paper. After
the parts desired are inked over the rest of the graphite print is
easily erased with an ordinary rubber.

By using this method it is possible to get absolute scale and more
satisfactory results than by tracing over a photographic print line
for line or by using a pantograph.

Requisitions for celluloid prints are made on the form used for
requesting photolithographic work.

SKETCHING BY RETICULATION.

If the sheet bearing the design or matter to be copied may be marred
without objection it is ruled lightly into pencil squares of equal
size. Corresponding squares of the same size, larger, or smaller,
according to the size of the new drawing, are then ruled on the
drawing paper, and the work is sketched square by square. If the
original sheet may not be marred the same result can be obtained by
drawing the lines on a transparent oversheet. This method is
serviceable for enlarging or reducing simple work that includes no
great amount of detail; if great precision of detail is required the
original should be enlarged or reduced by photography or by the
pantograph.

THE "SHADOWLESS DRAFTING TABLE."

One of the most useful contrivances that has been made for tracing a
drawing on the same scale is called by its manufacturers the
"shadowless drafting table." The essential features of this table are
a wooden box inclosing strong incandescent lights and bearing a
ground-glass top. A drawing placed on the ground glass can be so
illuminated as to make its lines conspicuous and readily traceable
even through relatively thick paper. The table is particularly useful
for tracing sheets upon, which the lines are indistinct and would not
be discernible under tracing paper with reflected light. It is also
useful in preparing drawings in which certain features must register
perfectly over each other. In fact any drawing that does not require
enlarging or reducing can be traced with great facility by the use of
this drafting table, and it is particularly useful for tracing faint
lines on old and poorly preserved prints or drawings.

Such a table has been installed in the section of illustrations, where
it can be used by authors and others.


TOPOGRAPHIC FEATURES.

RELIEF.

The effect of relief is expressed on a map by three methods--by
contours, by hachures, and by shading. (See fig. 6.) The first method
does not give pronounced pictorial expression of relief, though it
gives correct shape and exact elevation; the others are mow pictorial,
but they do not give exact elevation.

_Contours._--As contoured maps are originally prepared from actual
surveys the draftsman should simply follow the copy furnished by the
topographer or such original matter as may be given to him for
redrawing. If the area mapped is large and the contours are close
together the original may be transferred by celluloid tracing (see p.
47), or it may be transferred by tracing with graphite-coated paper
(see p. 46). After the contour lines have been transferred they should
be traced in ink, in lines of even thickness, except those that
represent certain fixed intervals and are to be numbered, which should
be made slightly thicker. (See fig. 6, A.) In drawing these lines some
draftsmen use an ordinary ruling pen, others the swivel pen; but
considerable practice is required in the use of either before it can
be controlled to follow precisely the penciled lines. Still other
draftsmen use the Shepard pen or an ordinary drawing pen. The swivel
pen, if expertly handled, produces a firm and even line.

Italic numbers should be used to indicate the elevation of a contour
and should be placed in an opening in the line, never between lines.
Where the lines run close together great care should be taken that
they do not touch unless the interspaces are so narrow that they must
touch and combine. The lines should be firm and even, and if the copy
or original map shows that they are uniformly very close together it
should be enlarged before the tracing is made in order to give more
freedom in drawing; but if the enlarged map is to be much reduced care
should be taken to make the lines proportionate to the reduction. A
photo-engraving of a map on which the contour lines are drawn very
close together is likely to be unsatisfactory because, though the
spaces between the lines are reduced in width, the lines themselves
may show no corresponding reduction in thickness.

[Illustration: Figure 6.--Methods of expressing relief: (A) by contour
lines, (B) by hachures, (C) by shading on stipple board, and (D) by a
brush drawing. The four examples given represent the same area. The
drawings were made twice the size of the printed cuts.]

Certain contour lines are commonly accentuated on a map, generally
every fourth or fifth line--that is, for a 10-foot interval every
50-foot line, for a 20-foot interval every 100-foot line, for a
25-foot interval every 100-foot line, for a 50-foot interval every
250-foot line, and for a 100-foot interval every 500-foot line.

_Hachuring._--The effect of relief can be produced satisfactorily by
hachuring but only by a draftsman who has had considerable
well-directed practice in that kind of drawing. In a hachured map the
light should seem to come from the west or northwest--that is, the
darker parts should be on the east or southeast side of an elevation
and the lighter parts on the west or northwest The highest elevation
should be represented by the darkest shade on the right and by a
corresponding high light on the left. The hachuring should begin at
the crest of a peak, range, or butte and be worked downward toward the
gentler slopes, the lines being drawn farther apart and made thinner
until the floor of the valley is reached and the effect of shadow is
lost by fewer and lighter lines. On a hachured map that is made from a
contoured map somewhat definite differences of elevation may be
indicated by the intervals between the strokes, and abrupt changes in
slope may be indicated by shorter and heavier lines. The strokes
should be disjointed, and they should trend at right angles to the
upper margin of a cliff and should radiate from a peak. Figure 6, B,
represents satisfactory hachuring.

_Hill shading._--Relief is more easily expressed by shading than by
hachuring. (See fig. 6, C, D.) The draftsman can best express it by
this means after he has studied contoured maps or photographs of the
region mapped, if they are available, in order that he may obtain an
idea of the details of its topography.

The special means used to produce hill shading will depend on the
character of surface of the paper on which the drawing is to be made,
the size of the map, the amount of detail and refinement of execution
desired, and the amount of reduction to be made in reproducing the
drawing. For maps on which it is desired to show some refinement of
drawing and detail, a lithographic or wax crayon can be used on paper
which has a grained surface. The draftsman must express relief
according to the information he has at hand, whether detailed or
general, and must employ methods that accord with the purpose of the
map and the mode of reproduction selected. If a shaded relief map is
to be prepared for direct reproduction by photolithography and the
shading is to be printed in a separate color the base map should be
completed first and a light photographic or blue print obtained on
which to add the relief in black lithographic crayon, to insure
perfect fitting of the relief and the base; or the relief can be
prepared on an oversheet--a semitransparent white paper with
sufficient "tooth" or grain to cut the shading up into minute dots.
The shadowless drafting table (see p. 47) is especially useful for
this purpose. On this oversheet register marks should be placed at the
four comers and at several other points, particularly at the
intersection of parallels and meridians.

For relief shading on small black and white maps Ross's hand-stipple
drawing paper may be used. (See p. 24.) By rubbing a black wax crayon
or pencil over the surface of the paper the desired effect is produced
in fine dots or in stipple, which may be varied in density of shade at
the will of the draftsman. (See fig. 6, C.) High lights can be
produced by scraping away the chalky surface of the paper. A
lithographic or wax crayon is the best medium to use on this stipple
paper, as on the paper referred to in the preceding paragraph, for the
shading produced by it is not so easily smeared as that produced in
pastel or by a graphite pencil. The object of using either the rough
paper or Boss's stipple paper for drawings that are to be reproduced
by photo-engraving is to produce a shading that is broken up into dots
of varying sizes, which is essential in such reproduction.

Belief shading for maps can also be made with a brush in flat washes
of either india ink or lampblack. Such shading should be made only
over a blue print or an impression of some kind from the map upon
which the shading or relief is to be overprinted. If the relief is
expressed on the author's original by contours the general shapes of
the relief and the drainage lines can be traced and transferred
lightly in blue lines to form a base on which to model the shading and
at the same time to make the shading fit the streams. Such a drawing
can be photographed through a screen and reproduced by half tone (see
fig. 6, D) or mezzotint as a separate plate made to overprint the map
in another color.

HYDROGRAPHY.

_General directions._--The drainage features of a map should be so
drawn as to suggest the natural courses of the streams. Streams should
not be drawn in straight, hard lines, as such lines are decidedly
unnatural and produce a crude effect. The course of a river may be
straight in general, but it is likely to be somewhat sinuous in
detail. If the streams shown on a preliminary map are drawn in a
clumsy or characterless fashion they should be redrawn with a freehand
effect or made slightly wavy, in order that they may appear more
natural. The gradual widening of streams from source to mouth should
also be shown in the drawing. On small-scale maps, where the eye can
at once see a stream through its full length, this almost
imperceptible widening can be expressed by a line of almost uniform
weight except for the stretch near the source, where it should grow
thinner and taper off. On maps which are to be reproduced directly
from drawings in black and white and which are to show both contour
lines and drainage the lines representing the streams and other water
bodies should generally be drawn freehand and slightly heavier than
the contour lines, which should be sharper and more precise.

The names of all streams or other bodies of water should be in italic
letters, those of the larger streams being lettered in capitals and
those of the smaller streams in capitals and lower-case letters. (See
"Lettering," p. 53.)

_Water lining._--The use of water lining on black and white maps
should be limited to maps on which the water areas are not readily
distinguishable from the land areas. In rough drawings that are to
serve only as copy for engravers a flat color may be used for water
areas and its conversion into water lines specified. In base maps to
be reproduced in three colors a light-blue tint may be used in lieu of
water lining, and it can be printed either flat or in a fine ruling
transferred to the stone that is to print the drainage. The engraving
of water lines is expensive, and the flat blue color should generally
be preferred.

Water lining usually consists of 30 to 45 lines on engraved or large
maps, but on small maps and sketch maps the number may be reduced as
desired. Care should be taken that the lines are as nearly parallel as
they can be made freehand and of even weight or thickness. The first
three to six lines outside the coast line should be somewhat closer
together than those farther out and should conform closely to the
coast line, but the spacing between the lines should increase and the
lines should become almost imperceptibly less conformable to the coast
line as they reach their outer limit, the last three to six being made
with the greatest care and refinement. Water-lined maps that are to be
reproduced by photographic processes should be drawn at least twice
publication size. The reduction will bring the lines closer together,
and the reproduction will show a more refined effect than could
possibly be produced by the most skillful drawing.

Good examples of water lining, such as are shown on the topographic
atlas sheets of the Survey, should be studied by draftsmen before
they undertake such work.

[Illustration: U. S. GEOLOGICAL SURVEY

PREPARATION OF ILLUSTRATIONS PLATE IV


SYMBOLS USED ON BASE MAPS]


CULTURAL FEATURES.

The cultural features represented on a map include "the works of
man"--not only cities, towns, buildings, bridges, railroads, and other
roads, but State, county, and other boundary lines--in short, all that
part of a three-color base map which is shown in black, the engraved
plate for the black being called the culture plate. The features named
in the list below are the cultural features referred to. (See PL IV
for corresponding symbols.)

Aqueduct mains.
Aqueduct tunnels.
Bench marks.
Boundary Lines.
Boundary monuments.
Breakwaters.
Bridges.
Buildings.
Cable Lines.
Camps.
Canal locks.
Canals.
Cemeteries.
Churches.
Cities.
County lines.
Dams.
District lines.
Ditches.
Electric power lines.
Fences.
Ferries.
Fords.
Gas wells.
Hedges.

Hospitals.
Jetties.
Land-grant lines.
Land-section Lines.
Levees.
Mains.
Mineral monuments.
Mine tunnels.
Mines.
National forests.
National parks.
Oil tanks.
Oil wells.
Open cuts.
Park boundaries.
Paths.
Pits.
Post offices.
Precinct lines.
Prospects.
Province lines.
Quarries.
Quarter-section lines.
Railroads, steam or electric.

Ranches.
Reservation boundaries.
Reservoirs.
Roads.
Ruins.
Schoolhouses.
Section comers.
Section Lines.
Settlements.
Shafts.
Streets.
Telegraph Lines.
Towns.
Township comers.
Townships.
Trails.
Tramways.
Triangulation stations.
Tunnels.
Villages.
Water mains.
Water wells.
Waterworks.
Windmills.


LETTERING.

GENERAL DIRECTIONS.

The cultural features are named on maps by letters of two distinct
styles--slanting gothic for public works and roman for habitations and
civil divisions. The size of the letters used should indicate in a
general way the relative importance of the feature or group to which
they are applied, but on some maps the county seats, State capitals,
and large cities may be distinguished by different symbols. The names
of civil divisions are lettered in sizes depending on their relative
grade and the size of the area or space in which the names are to
appear.

The features shown on a topographic map may be broadly separated into
four groups and are lettered as follows:

Civil divisions (countries, States, counties, townships, land grants,
reservations, cities, towns, villages, settlements, schools, lodges,
ranches, etc.), roman capitals or capitals and lower case.

Public works (railroads, tunnels, roads, canals, ferries, bridges,
fords, dams, mains, mines, forts, trails, etc.), slanting gothic
capitals (light) or capitals and lower case.

Hydrographic features (oceans, seas, gulfs, bays, lakes, ponds,
rivers, creeks, brooks, springs, wells, falls, rapids, marshes,
glaciers, etc.), italic capitals or capitals and lower case.

Hypsographic features (mountains, ranges, peaks, plateaus, cliffs,
buttes, canyons, valleys, peninsulas, islands, capes, etc.), upright
gothic capitals (light) or capitals and lower case.

The essential principles of lettering have been described in numerous
treatises and are well understood by most draftsmen. The correct form
of each letter may be learned from such treatises, but spacing and
arrangement are best learned by observation and experience. Good
lettering will not strongly attract attention, but even slight
imperfections of form, spacing, slant, and shading will be quickly
detected and criticized. Map letterers should note that the name of a
place or the number of a symbol should be put to the right of the
symbol if possible and a little above or below it--not to the left and
directly on a line with it, as Tucson=o=, 17=o=, Dallas=o=, Carson=o=.
Names indicating large areas, if written from west to east, should
curve with the parallels, and all names should be so lettered that "if
they should fall they would fall on their feet." Every name should be
distinctly legible but not so conspicuous as to subordinate the
feature it designates. Lines should therefore not be broken in order
to make the lettering clear except where there is possible danger that
the smaller spaces may be filled up in printing. The lettering on a
map should always be so spaced that it will properly fit the area it
is intended to designate. In names consisting of two or more words the
letters should not be closely spaced if wide spaces are left between
the words. In numbers, except those used to indicate elevations on
contour Lines or elsewhere, thousands should always be set off by
commas.

Draftsmen often draw bad forms for commas, quotation marks,
apostrophes, and question marks. The following forms are correct:
Comma , ; quotation marks "" ; apostrophe ' ; question mark ? .

LETTERING BY TYPE.

Names and short notes printed from type on paper, to be cut out and
pasted in proper positions on maps or other drawings, now furnish a
large proportion of the lettering on the Survey's illustrations. The
strips are likely to become detached by the repeated handling of a
drawing, however, unless they are securely pasted on. The best results
can be obtained by having the type printed on a special brand of
"noncurling" gummed paper, from which the lettering is cut in squares
or strips, which are dampened and applied to the proper places on the
drawing. In handling such strips a pair of dentist's tweezers is
useful. When mucilage is applied to printed strips of ordinary paper
the moisture causes the paper to warp or curl, often so much as to
affect the reproduction of the drawing. This printed lettering is
generally used, however, only for headings, titles, notes, and other
matter that stands alone; it should not be used for the geographic
names in the body of a map unless only a few names are to appear, for
the strips of paper bearing the names may obscure parts of the map.
The reproduction of this lettering by photo-engraving or
photolithography gives results superior to those obtained from hand
lettering unless each letter is made with the utmost care, work which
is considered a waste of time.

[Illustration: U. S. GEOLOGICAL SURVEY

PREPARATION OF ILLUSTRATIONS PLATE V


REDUCTION SHEET USED IN LETTERING ILLUSTRATIONS.

The largest size shows the letters unreduced; the other sizes show
the letters reduced as indicated in the margin.]

Type is used also for printing lettering directly on a drawing exactly
in proper position, by a special type holder, somewhat like a
self-inking stamp.

Most of the styles and sizes of type now used on maps in the Survey's
reports are shown in Plate V.

If a drawing is to be reduced one-half the smallest type used should
be about 2 millimeters in height; if it is to be reduced one-third the
smallest type used should be about 1.5 millimeters in height; and so
on. No letter whose vertical height after reproduction would be less
than about 1 millimeter should be used, and the larger lettering
should bear a proper relation to the smaller. Sheets showing the
styles of type in use by the Survey, in full size and reduced
one-fourth, one-third, two-fifths, one-half, three-fifths, two-thirds,
and three-fourths, will be furnished on request. If a drawing is to be
reduced one-half, for example, the sheet that has been reduced
one-half will show the size of the lettering on the printed plate, so
that the draftsman, by referring to the sheet showing the reduction he
desires, can select type of a size that will be legible. Plate V shows
a part of this reduction sheet.

ABBREVIATIONS.

The following are the correct forms for abbreviations used on maps and
other illustrations:

A.        Arroyo.
B. M.     Bench mark.
Bdy.      Boundary.
Br.       Branch, bridge.
C.        Cape.
Can.      Canal, canyon.
Cem.      Cemetery.
Co.       County.
Cr.       Creek.
E.        East.
El.       Elevation.
Est.      Estuary.
Fk.       Fork.
Ft.       Fort, foot.
Gl.       Gulch, glacier.
Hrb.      Harbor.
I.        Island.
Is.       Islands.
Jc.       Junction.
L.        Lake.
Lat.      Latitude.
Ldg.      Landing.
L. S. S.  Life-saving station.
L. H.     Lighthouse.
Long.     Longitude.
M. P.     Milepost.
M. M.     Mineral monument.
Mt.       Mount.
Mtn.      Mountain.
Mts.      Mountains.
N.        North.
Pen.      Peninsula.
Pk.       Peak.
P. O.     Post office.
Pt.       Point.
R.        Range, river.
Res.      Reservation, reservoir.
R. H.     Road house.
S.        South.
Sd.       Sound.
S. H.     Schoolhouse.
Sta.      Station.
Str.      Stream.
T.        Township.
Tel.      Telegraph.
W.        West.

Words like mount, river, point should not be abbreviated where they
form a part of the name of a city or town, as Rocky Mount, Fall River,
West Point. Neither the word nor the abbreviation for railroad or
railway should be placed on a map; the chartered name (or initials of
the name) and the road symbol are sufficient.

Names of States and Territories should be abbreviated, where
abbreviation is necessary, as follows:

Ala.     Ga.      Minn.    N. J.    Tenn.
Ariz.    Ill.     Miss.    N. Mex.  Tex.
Ark.     Ind.     Mo.      N. Y.    Va.
Calif.   Kans.    Mont.    Okla.    Vt.
Colo.    Ky.      Nebr.    Oreg.    Wash.
Conn.    La.      Nev.     Pa.      W. Va
D. C.    Mass.    N. C.    R. I.    Wis.
Del.     Md.      N. Dak.  S. C.    Wyo.
Fla.     Mich.    N. H.    S. Dak.

Alaska, Guam, Hawaii, Idaho, Iowa, Maine, Ohio, Samoa, and Utah should
be written in full.

The abbreviations used on the margins of maps for subdivisions of land
should be as follows (note punctuation): T. 2 N., E. 3 W. On
large-scale plats the marginal lettering should be as follows: N. 1/2
NE. 1/4 sec. 1, T. 7 N., K 2 W.; fractional secs. 2 and 35, Tps. 7 and
8 N., R. 2 W.; NW. 1/4 sec. 20, T, 7 N., R. 2 W. In spelling fractions
use half and quarter, not one-half and one-quarter.

The abbreviated forms of such names as North Fork and South Fork
should be N. Fork and S. Fork, not North Fk. and South Fk.

Additional abbreviations used on illustrations are as follows:

  N. for north, NE. for northeast, NNE. for north-northeast, etc.
    Capitalize directions affixed to street names, as NW., SE.
    (1800 F St. NW.).

  Sec. and secs. for section and sections before a number.
    Capitalize only at the beginning of a line or sentence.

  a. m. and p. m. for antemeridian and postmeridian, as 4.30 p. m.
    Lower-case unless in line of caps.

  & in names of corporations or companies. On Survey miscellaneous
    maps "and" is spelled out in railroad names.

  B. t. u. for British thermal units.

  bbl., bbls. for barrel, barrels.

  bu. for bushel or bushels.

  c. c. for cubic centimeter.

  cm. for centimeter.

  cwt. for hundredweight.

  dwt. or pwt. for pennyweight

  oz. for ounce or ounces.

  etc. (not &c.) for et cetera.

  ft. for foot or feet.

  H. m. s. for hours, minutes, and seconds. (Use capital H.)

  in. for inch or inches.

  kw. for kilowatt or kilowatts.

  £ s. d. for pounds, shillings, and pence.

  per cent (omitting period) for per centum. Spell out percentage.

  ser. for series.

  St. for Saint or street

  U. S. Army for United States Army, as distinguished from United
    States of America (U. S. A.).

  yd., yds. for yard, yards.

[Illustration: U. S. GEOLOGICAL SURVEY

PREPARATION OF ILLUSTRATIONS PLATE VI


  175-LINE SCREEN  150-LINE SCREEN

  133-LINE SCREEN  120-LINE SCREEN

  100-LINE SCREEN   65-LINE SCREEN

HALF-TONE CUTS SHOWING EFFECT OF SEVERAL STANDARD SCREENS IN THE
REPRODUCTION OF THE SAME DETAIL.]

The names of certain months may in some places be abbreviated; those
of others should invariably be spelled out. The following are the
correct forms:

  Jan.    Apr.    July    Oct.
  Feb.    May     Aug.    Nov.
  Mar.    June    Sept    Dec.

The abbreviations for number and numbers before figures are No. and
Nos. The o should never be raised, as in N^o. The abbreviation for Mac
is Mc, not M^c.

All periods should be omitted from abbreviations used in the body of a
map unless their omission would cause misunderstanding. They are
generally unnecessary, and if used on some maps they are likely to be
mistaken for symbols representing certain features, such as houses or
flowing wells, if either is shown. Periods used on drawings that are
to be reproduced "direct" or photomechanically should always be
slightly exaggerated.

NAMES OF RAILROADS.

The names of railroads may be written in full or abbreviated, in
accordance with the kind of map and the space available. On a sketch
map in black and white the initial letters are generally sufficient.
On a more detailed map, if there is room enough, the names may be
spelled out. As already stated, neither the words "railroad" and
"railway" nor the abbreviations R. R. and Ry. should be used on a map.


MAKE-UP OF MAPS.

FORMS FOR CERTAIN FEATURES.

The proper forms for certain features of maps, such as the borders,
titles, explanations, bar scales, captions, arrows indicating true
north and magnetic declination, source, and authorship, are shown in
Plate VII. Note particularly the style and position of the marginal
matter.

BORDER.

A finished map border is used or omitted according to the kind of map
prepared. Diagrammatic maps and maps on which no parallels and
meridians appear do not need finished borders. On a map that shows
complete areal geologic or other coloring, such as a map in a Survey
geologic folio, the border lines tend to destroy the simple effect of
the whole map. On a map that is not completely colored and on all very
large maps borders are really necessary. If borders are used, however,
the space between the neat line and the outer line of the border
should be only sufficient to provide proper space for the numbers
showing latitude and longitude or township and range. A simple rule[8]
for determining the width of this space is as follows: Divide the sum
of the dimensions of the map by 2 and find the square root of the
quotient, which will represent the width of the border in sixteenths
of an inch. Example: Map is 20 by 30 inches; (20 + 30)/2 = 25; square
root of 25 = 5; width of border = 5/16 inch.

[Footnote 8: Worked out by Martin Solem, of the U. S. Geological
Survey.]

The numbers showing latitude and longitude should be in shaded arabic
numerals and those showing township and range in gothic. The symbols
for degree, minute, and second should not be crowded. On a map that
has no added border lines the numbers should be in hair-line gothic.

TITLE.

The title of a map should be in roman letters and if placed at the
lower margin should generally be arranged in two lines, unless it is
short. If it forms two or more lines the lines should be well
balanced. The first line should describe the position of the area; the
second line should state the purpose of the map, as

    MAP OF BUTTE AND VICINITY, MONTANA

    SHOWING LOCATION OF MINES AND PROSPECTS.

A title placed inside the border of a map should be arranged in a
series of lines, generally beginning with "Map of" or "Geologic map
of." and the line showing the dominant part of the title should be
emphasized by larger lettering, thus:

                                 =MAP OF=
                             THE VICINITY OF BUTTE
                                    MONTANA
                    SHOWING LOCATION OF MINES AND PROSPECTS.

The name of the author or compiler of a map or of the person supplying
the geologic or other data shown on it may be placed either beneath
the title or in the lower right corner, just below the border line,
and the names of the topographers or the source of the base should be
stated in the lower left corner, just below the border line. If the
title is placed inside the border all notes giving credit for any part
or features of the map may be placed beneath the title or scale. (See
PI. VII.)

[Illustration: U. S. GEOLOGICAL SURVEY

PREPARATION OF ILLUSTRATIONS PLATE VII


DETAILS OF THE MAKE-UP OF A GEOLOGIC MAP]

EXPLANATION.

The symbols, patterns, or colors used on a map should be given in a
series of rectangles or "boxes," accompanied by explanatory terms in
the form shown in Plate VII, headed "Explanation." If the explanation
is small a convenient place for it on some maps may be found within
the neat lines. If no space is available there, or if it is so large
that there is not room to place it there without obscuring other
details, it may be placed either vertically along the right margin, as
shown in Plate VII, or horizontally under the title. A geologic
explanation should preferably be arranged vertically, as in Plate VII,
so as to show the relative age of the formations by the positions of
the boxes. This explanation should be carefully worked out in pencil
by the draftsman and approved by the committee on geologic names
before it is drawn in ink, in order to save time in making
corrections.

In lettering the explanation roman letters or type should be used for
the titles under the boxes and italic of smaller size for the
subtitles or descriptive detail, which should be inclosed in
parentheses. The names of geologic periods and systems should be in
gothic capitals, the names of series or groups should be in italic
lower case, and the limit of each period, system, or group should be
indicated by braces. The general style and arrangement shown in the
Survey's geologic folios should be followed, and this and the
arrangement of other matter is shown in Plate VII. Care should be
taken not to crowd the explanation, and if corrections are necessary
they should be so made that each line of the matter in which they
appear will be properly spaced.

The explanation for a map that is to be engraved or to be reproduced
by lithography need only be sketched in to show general style and
arrangement. The engraver or the lithographer will supply such matter
in proper form according to specifications. For direct reproduction,
however, as by photolithography or zinc etching, the lettering must
either be carefully drawn with pen or printed from type on slips,
which are pasted on the drawing.

GRAPHIC SCALES FOR MAPS.

A bar scale for miles or feet should be given on every map, and if the
map is of international interest the metric scale should be given just
beneath the scale of miles or feet. The accepted designs for these
scales are shown in figure 7. The scale should be accompanied by any
necessary statement pertaining to the base map, such as "Contour
interval 20 feet," "Datum is mean sea level." The fractional scale
(1/250,000, for example) should be given on all except the more simple
kinds of maps, and the date of publication should also appear just
below the scale or scales. The single-line bar scale should be used
only on small or simple maps. The length of the bar scale must depend
on the size of the map and the space available. Those shown in figure
7 were made over blue prints from scales used by the Survey.

To make a bar scale for a map of unknown scale that shows only a
single meridian and parallel, or for a map on which no meridians or
parallels are shown, first ascertain the distance between two points
shown on the map by reference to other authentic maps. If, for
example, the distance between two such points is 16.315 miles draw a
horizontal line (_a_ in fig. 8) representing this distance on the map,
and at its end, at right angles to it, draw another line (_b_)
actually measuring 16.315 units of any convenient denomination. Draw a
straight line (c) diagonally between the ends of lines _a_ and _b_.
Then set off on line _b_ any convenient number of the units selected,
say 5 or 10, and project from the points set off lines exactly
parallel with line _c_ to line _a_. The distance and the number of the
units thus marked on line a will indicate the number of miles covered
by that distance on the map, as shown in figure 8.

[Illustration: Figure 7.--Designs for bar scales.]

[Illustration: Figure 8.--Method of making a bar scale for a map of
unknown scale.]

[Illustration: U. S. GEOLOGICAL SURVEY

PREPARATION OF ILLUSTRATIONS PLATE VIII


PATTERNS USED TO SHOW DISTINCTIONS BETWEEN AREAS ON BLACK AND WHITE
MAPS

Contrasts may be increased by varying the direction and spacing of
Lines]

SYMBOLS.

Symbols should be drawn with as much care as letters, though to a
critic they may not appear so bad as poor lettering unless he finds
them glaringly large or so small that he can discover or identify them
only with difficulty. The size of a symbol must depend on its
importance on the map bearing it. On a map that shows numerous mines,
for instance, the crossed hammers or the symbols for shafts should be
not only visible but conspicuous. The draftsman who is to make such a
map must know beforehand how much his drawing will be reduced in
reproduction and must make the symbols in proportion to the reduction.
The symbols shown in Plate II (p. 20) should be used in all the
Survey's illustrations where they are appropriate.

AREAL PATTERNS FOR BLACK AND WHITE MAPS.

The conventional patterns used on a map to distinguish separate areas,
chiefly geologic, are shown in Plate VIII. The patterns shown
represent the proper combinations of lines, dots, and other forms and
should be spaced openly or closely according to the size of the area
covered, the contrast needed between areas, and the general clearness
and effect desired. If a map is to show both small and large areas
dense or closely spaced patterns should generally be used for the
smaller areas, even if they may be required for some fairly large
areas representing the same formation or condition. On the other hand,
open patterns should be used for large areas. Again, it may be
necessary to make certain areas more conspicuous than others, and this
effect can be best produced by drawing the lines closer together
rather than by making them heavier, unless the area covered is small
or unless a closely spaced similar pattern has been or will be used
elsewhere on the map. Heavy-line patterns or bars are not desirable.
The lines forming a pattern should generally be drawn at an angle of
45° to the sides of the map; they should be drawn vertically or
horizontally only in small areas or in areas not crossed by meridians
or parallels or by other lines running in the same direction. The
lines should preferably run across the long axis of an area, not
parallel to it, and the predominating trend or general direction of
the areas of one geologic formation on a map should decide the
direction of the lines for all areas of that formation on the same
map, even if the rule must be violated on some of the minor areas.

An effort should always be made to produce a pattern that is
subordinate in strength to the main lines of the base map on which it
is drawn. In black and white maps, as in colored maps, unlike patterns
should be placed next to each other. If they are so placed it may not
be necessary to rule the lines on two adjacent areas in opposite
directions to produce needed distinctions. A section liner or other
ruling device should be used in drawing line patterns in order to
produce uniformly even spacing. The application of six of these
conventional patterns to a base map is shown in figure 9.

[Illustration: Figure 9.--Map bearing six areal line patterns.]

STANDARD COLORS FOR GEOLOGIC MAPS.

The standard series of colors for systems of sedimentary rocks is
shown on the maps in the Survey's geologic folios but is subject to
modifications for use on maps in other Survey reports. Each system is
represented by a different color, and if there are two or more
formations in one system they are generally distinguished by using
different patterns composed of straight parallel lines in the same
color. The patterns for subaerial deposits (chiefly Quaternary) are
composed of dots or circles, or combinations of both, and may be
printed in any color, but the color most often used is yellow or
ochraceous orange. No specific colors are prescribed for igneous
rocks, but if only a few areas are shown red or pink is preferred. The
colors used for igneous rocks are generally more brilliant and purer
than those used for sedimentary rocks. For small areas they are used
"solid"; for large areas they are reduced in tone by the use of a
suitable cross-line pattern or "reticle." Metamorphic rocks are
represented by short dashes irregularly placed. These dashes may be in
black or in color over a ground tint or over an uncolored area, or
they may be in white on a ground tint or pattern. The standard colors
used for the sedimentary series covering the 12 systems recognized by
the Geological Survey are: Quaternary (Q), ochraceous orange; Tertiary
(T), _yellow ocher_ and _isabella color_; Cretaceous (K),
_olive-green_ or _rainette-green_; Jurassic (J), _blue-green_ or
_niagara-green_; Triassic (TR), _light peacock-blue_ or _bluish
gray-green_; Carboniferous (C), _blue_ or _columibia-blue_; Devonian
(D), _gray-purple_ or _heliotrope-gray_; Silurian (S), _purple_ or
_argyle-purple_; Ordovician (0), _red-purple_ or _rocellin-purple_;
Cambrian (-C), _brick-red_ or _etruscan red_; Algonkian (A), _terra
cotta_ or _onion-skin pink_; Archean (AR), _gray-brown_ or _drab_.[9]

[Footnote 9: Names printed in italic are from "Color standards and
nomenclature," by Robert Ridgway.]

REDUCTION OF ENLARGEMENT OF MAPS.

The following is the simplest and most accurate method of marking the
reduction or enlargement of a map to a selected scale: Measure the
distance between the extreme meridians along one of the parallels.
(See fig. 10.) Convert this distance into miles by multiplying the
number of degrees it covers (say 3) by the number of miles in a
degree. A degree on the forty-third parallel, for example, is 50.669
miles,[10] which multiplied by 3 equals 152.007 miles. Then draw a
line on the margin of the map, outside the border, the exact length of
the 3 degrees, and just below this line draw another line representing
the same number of miles (152.007) on the scale to which the map is to
be reduced or enlarged. Then mark to reduce or enlarge the upper line
to the lower line, as shown in figure 10. A long line will reduce
error and give greater accuracy than a short one, and therefore as
great a distance should be set off as possible. The number of miles
represented by both lines and the fractional scale to which it is to
be reduced should be stated on the drawing, for permanent record.

[Footnote 10: See U. S. Geol. Survey Bull. 650, p. 37. 1916.]

Maps that will bear reduction without affecting the clearness of the
details they show may be reduced to fit the book in which they are to
appear, regardless of definite scale. The reduction for such maps is
best marked in fractions, as "1/2 off," "1/3 off," "2/3 off." If the
size needed is not exactly represented by these fractions it should be
indicated in inches, as "Reduce this line to 7-1/2 inches," or "Reduce
to 4-3/8 inches in width."

[Illustration: Figure 10.--Diagram showing method of marking maps for
reduction or enlargement (for record).]


DIAGRAMS.

In preparing a diagram a draftsman should endeavor to make its parts
and relations perfectly clear to the reader. He should study the
drawing or material furnished by the author until he fully understands
it and should endeavor to reproduce it simply and legibly. Any
lettering that may be needed should generally be in plain upright or
slanting gothic type (see Pl. IX), or it may be in roman.

A diagram should generally be drawn on bristol board or on blue-lined
section paper and should be marked for reduction to the minimum size.
It should bear no title, as the title will be set up in type by the
printer.


SECTIONS.

The sections used in geologic reports are of two widely different
kinds. One shows only the broader relations of parts; the other shows
details of structure as well as relations. One is diagrammatic; the
other is more realistic and graphic. The draftsman should prepare all
sections strictly according to the copy supplied by the author but
should use proper symbols and make a more finished drawing. The
various kinds of sections, most of them geologic, are described on
pages 29-30, and the conventions used to express lithologic character
are shown in Plate III.

[Illustration: U. S. GEOLOGICAL SURVEY

PREPARATION OF ILLUSTRATIONS PLATE VIII


DIAGRAMS AND CURVES.]

Detailed drawings of this kind, though entirely conventional, can be
so prepared as to give a satisfactory expression of nature. The
draftsman should study well-prepared sections in Geological Survey
reports and should learn the details of folding and faulting from
textbooks. He should first ascertain whether or not the vertical scale
in the original section has been unduly exaggerated, and if so he
should confer with the author with a view to reducing the exaggeration
as much as possible. He should submit to the author all questions as
to doubtful points, as well as all suggestions for improvement in
expression, before he makes any changes, and he should make
corrections only on the author's approval. A seeming inaccuracy in an
author's drawing may be a faithful representation of natural
conditions. For example, a formation that seems to be omitted by
inadvertence in drawing may really "pinch out" at a point represented
in the section. (See a on fig. 11.)

[Illustration: Figure 11.--Structure section showing method of
determining the secession of folds.]

Penciled lines corresponding to those shown by dots in figure 11
should be carefully added in redrawing a roughly sketched section that
shows complex folding. An original indefinite sketch that shows
complicated structure affords opportunities for error in preparing the
new drawing, and omissions may be detected by following the formations
as they would be continued above and below the section, as shown by
the dotted lines in the figure.


PLANS AND CROSS SECTIONS OF MINES.

Plans of mines, like diagrams, should not be elaborate, and their
lettering should be plain and legible, yet it should not be so
conspicuous as to obscure other details. Gothic letters should
generally be used, but some plans require different styles of
lettering, especially for geographic or other names that should be
coordinate with those on maps or other illustrations in the book.
Unless there are good reasons, however, for varying the styles of
lettering, plain gothic capitals, or capitals and lower-case letters,
either upright or slanting, should be used. Abbreviations for the
numbers of levels should generally be given thus: 3d level, 6th level,
200-foot level, etc., or the shorter terms may be spelled out, as
third level, sixth level. The same general scheme of lettering should
be used on all plans and cross sections that are to appear in one
publication or in one series of similar papers.

The reduction of such drawings to the minimum scale consistent with
clearness is always advisable.




DRAWINGS OF SPECIMENS OF ROCKS AND FOSSILS.


METHODS USED.

Drawings of specimens or other objects were once made with brush and
pencil or with pen and ink, by means of measurements taken with
dividers or by viewing the specimen through a camera lucida. Each of
these methods is still used, but by using the camera lucida in
sketching: the outlines and details more accurate proportions and
relations can be produced, whether the object is to be enlarged or
reduced, than by any other means except photography.


BRUSH AND PENCIL DRAWINGS.

In all drawings or photographs of specimens, except photomicrographs
of thin sections, the light should appear to come from the upper left
quarter. A disregard of the well-established rule that the direction
of illumination should be uniform throughout a series of drawings
would cause confusion or uncertainty in the interpretation of the
relief shown in them.

Reynolds's three-ply and four-ply bristol board affords a satisfactory
surface for brush and pencil drawings. Its surface is smooth and hard
and, being free from coating of any kind, permits satisfactory
erasures without great injury; its color is pure whits; and it is
durable.

Boss's relief hand-stipple paper is also well adapted to many kinds of
brush drawings as well as to its primary use for producing stippled
effects. Very delicate gradations of color or light and shade can be
produced on its surface with brush and lampblack or with india ink,
and high lights can be made by scraping off the chalky surface.

The draftsman who is preparing brush and pencil drawings should have
first of all a knowledge of the principles of light and shade, of
reflected light, and (for drawing specimens) of shadow perspective. He
should also have delicacy of touch and ability to see and interpret
form and to reproduce the soft blending of light and shade shown in a
good photograph. He should be provided with pencils equal in quality
to the Koh-i-noor B, F, 4H, and 6H; the best quality of red sable
brushes of the sizes of Winsor & Newton's Nos. 3, 4, and 6; the best
quality of stick india ink; a cake or pan of lampblack; and a
porcelain saucer or slab.

In drawings of fossils and of some other specimens a combination of
pencil and brush work produces satisfactory results and tends to
increase speed. The gloss produced by penciling, however, is
objectionable and should be obviated by a preponderance of brush work.
Stick India ink is the best pigment to use in delicate wash drawings,
and lampblack is preferable for large work on which the softer tones
of the shading are not so important and for drawings that are to be
considerably reduced when engraved. Gouache (an opaque mixture of
Chinese white and lampblack) may also be used, but it is best suited
for large work.

In making corrections on brush drawings the parts to be corrected
should be carefully washed out with a small short-cropped brush and
water and still further cleaned by using a rubber eraser over an
erasing shield or an opening cut in a piece of celluloid. Erasures
should not be made on delicate work with a knife or a sand rubber, as
either will injure the surface and affect reproduction. In measuring a
specimen with dividers the draftsman should be careful not to injure
the specimen or to puncture the paper on which he is preparing the
drawing.


PEN DRAWINGS.

A draftsman who is preparing drawings of specimens with pen and ink
should have a good assortment of pens equal to Gillott's Nos. 291,
290, and 170, liquid waterproof ink equal to that manufactured by
Higgins, good pencils, hard and soft rubber erasures, plain dividers,
and Reynolds's bristol board. A glass eraser is also useful.

Good pen drawings of specimens are much more difficult to make than
brush drawings. They can be prepared only by a draftsman who has had
some artistic training and experience in pen work. Few draftsmen can
prepare pen drawings that faithfully represent both the detail and the
texture of specimens; the shading on many such drawings confuses and
destroys both detail and texture.

The pencil sketch over which a pen drawing of a specimen should be
made must be prepared in much the same manner as the sketch for a
brush drawing, though the outlines need not be so delicate. This
sketch is generally made on bristol board. The pen work should begin
with the outlines and should then be carried to the details, and
finally to the shading, whether in lines or stipple. The texture of a
specimen is the best key to the proper shading. If the specimen is
decidedly granular, stippling is appropriate; if it is smooth or
polished, finely drawn parallel lines, varied in spacing and
character according to depth of shade and texture, are preferable.
Erasures can be made with a hard-rubber eraser, other parts being
protected by a shield, or with a very sharp knife or a glass eraser,
and the parts erased can be resurfaced with an agate burnisher.




RETOUCHING PHOTOGRAPHS OF SPECIMENS.


Photographs of specimens, particularly fossils that have been coated
to destroy local color, should be printed on velox paper, in a tone
somewhat lighter than that of ordinary photographs. The details and
relief should, however, be strong enough to enable the draftsman to
see them clearly, so that by retouching them and strengthening the
shadows and high lights he can make them sufficiently strong for
reproduction. This he can do by a combination of pencil and brush
work, the pencil being used sparingly because the gloss produced by
the graphite is likely to affect reproduction. A No. 3 Winsor &
Newton's red sable brush and lampblack are preferable for the greater
part of this work, and a 4H and a 6H pencil for the fine details and
as a possible aid in producing the finer gradations of shading. The
details should be retouched or strengthened under a reading glass to
insure accuracy; the broader effects can be best produced without the
aid of a magnifier.

Erasures on photographs of specimens should be made very carefully
with a hard rubber that is free from sand, and the parts not to be
disturbed should be protected with a shield. High lights may be added
by carefully scraping or rubbing the surface of the paper.




LANDSCAPE DRAWINGS FROM POOR PHOTOGRAPHS.


A poor photograph or one that has become injured and can not be
retouched for direct reproduction can be utilized by making from it,
as described below, a pen drawing or a brush or crayon drawing, which
will be almost photographically correct.


PEN DRAWINGS MADE OVER PHOTOGRAPHS.

A pen and ink drawing may be made over a blue print or a bromide print
(preferably a blue print) and the photographic image then bleached
out. The blue print should be larger than publication size and should
not be so dark that the draftsman can not see his lines. If the
negative is available a bromide enlargement can be obtained; otherwise
the picture should be rephotographed in larger size, preferably twice
publication size. The enlargement will give the draftsman greater
freedom in drawing details and will make his work appear finer and
better in the reduced illustration. If the photographic print is of a
subject requiring the use of instruments it should be securely
fastened to a drawing board, square with the board, so that any
horizontal and vertical lines in it may be ruled by the use of a =T=
square and triangle. For specimen or landscape work it need not be
fastened.

For bleaching blue prints a saturated solution of oxalate of potassium
(K2C2O4 + H2O) has been used with good results. For bleaching bromide
prints cyanide of potassium (KCN) to which a few drops or flakes of
iodine have been added should be used. Neither kind of print should be
bleached until the drawing has been completely finished in every
detail, because bleaching loosens the fibers of the paper, so that the
ink of any added lines is likely to spread. The print should be placed
in a hard-rubber pan, the bleaching solution poured on it, and the pan
rocked until the image disappears. The print should then be carefully
removed, thoroughly washed in running water, placed between clean
white blotters to dry, and finally mounted on cardboard. For
temporary, hurried work on drawings that are not to be retained for
future use the blue print may be mounted first and bleached by pouring
the bleaching fluid over the mounted print.


BRUSH DRAWINGS FROM POOR PHOTOGRAPHS.

Brush drawings may be made directly from photographs by working over
an enlarged print with gouache, or by making a pencil tracing and
sketch of the photograph and working it up with lampblack or india
ink. The photograph should be larger than publication size to permit
greater freedom and breadth in drawing details. The larger size will
also afford a more refined and better engraving when reduced. If
lampblack or india ink is used and the subject is small, bristol board
is recommended, but if the photograph is larger than, say, 8 by 10
inches, Whatman's hot-pressed double elephant or similar paper, laid
down with thumb tacks, will prove satisfactory.

If gouache is used over a print a preliminary drawing is of course
unnecessary, but the photograph should be an unglazed print of a size
that will require considerable reduction, and the finished drawing
should be protected by an oversheet. If lampblack or india ink and not
gouache is used the photograph should be traced and a fairly complete
pencil sketch should be made before the brush is used.

Plates I, IV, _A_, V, _B_, and VII, _B_, Monograph 34, were made from
gouache drawings. Plates III, _A_, VII, _A_, X, XI, XII, XIII, XX,
XXVIII, and XXX, in the same publication, were made from lampblack or
india-ink wash drawings. The originals can be examined at any time.




OUTDOOR SKETCHES.


The art of sketching from nature is one in which few but professional
artists excel. Not many geologists are able to make sketches from
nature that are suitable for direct reproduction. An artistic
draftsman should be able to redraw the geologist's sketches, however,
in their true perspective and relations, with the skill necessary to
make them satisfactory illustrations.

In most crude outdoor sketches the important features are usually
shown with sufficient clearness to follow. If they are not the
draftsman should ascertain what those features are and prepare the new
drawing in such a way as to display them properly. The new drawing
should be made with pen and ink, generally for reduction to a text
figure, which is the most appropriate form for such an illustration.

In all sketches of this kind the lines should be drawn in such a way
as to produce natural effects and at the same time to make good
printing plates. Good examples of pen and ink sketches of this class
can be found in Monograph 34, already referred to, and in the Seventh
Annual Report, especially Plates XXVIII and XXXVIII; Ninth Annual
Report, Plates XLIII and XLIV; Tenth Annual Report, Plates XIV and XIX
and figure 58; Eleventh Annual Report, Plates XV, XXVII, XXXV, LII,
and LIV and figures 18, 30, 31, 67, 98, and 99.




DRAWINGS OF CRYSTALS.


A crystal should generally be drawn in outline with straight lines.
The invisible rear side of a crystal, if shown, should be represented
by dashed lines. The outer boundary line of a crystal should be
slightly heavier than the inside lines, which should all be of the
same weight. Striations should be shown by straight lines; broken or
uneven surfaces by irregular lines. A twinning line, if an
intersection edge, should be solid; if not an intersection edge it
should be broken into dashes. Italic, Greek, German, and Old English
letters are used to mark crystal faces. All faces of a given form
should be marked by the same letter but may be differentiated, if
necessary, by primes or numerals, thus: m, m', m'', m''', m{'v}.
"Leaders" should be short full lines, or, if these are likely to be
confusing, they should be dashes. Numbers may be used in place of
letters for specific purposes. Letters indicating twin faces are
underscored; a second twin is doubly underscored or overscored, thus:
m_, m=, m¯. Twin units may be differentiated by the use of roman
numerals.




RETOUCHING PHOTOGRAPHS.


An author, of course, selects his photographs to illustrate some
special features; he does not always consider their fitness for
reproduction. Photographs that are blurred or out of focus, those in
which the shadows are too black or lack transparency, and those which
have local defects, such as bad skies or spots, must be worked over to
make them suitable for reproduction. In order to remedy these defects
and produce natural results the draftsman doing work of this sort
should be able to see and interpret nature properly and to supply
natural effects in a manner corresponding with those produced
photographically. He should be sufficiently expert with the brush and
pencil and in handling an air brush to duplicate the delicate and soft
tones in the photograph, and he should know how the pigments he uses
will "take" when the subject is reproduced.

The retoucher should have access to an air brush and should provide
himself with a jar of photo white or blanc d'argent and a color box
containing indian red, crimson lake, yellow ocher, lampblack, and
ultramarine--colors with which he can duplicate those shown in any
photograph. He should also have the best grade of red sable brushes,
ranging in size from No. 3 to No. 8, a stack of porcelain saucers, and
a jar of oxgall. By mixing the colors to match exactly the shades of a
photograph and using a red sable brush he can strengthen details,
"spot out" flaws, and remove imperfections, except those in skies or
other large, flat areas, for which he must use an air brush.

The air brush has become a necessary adjunct to a retoucher's outfit.
Smooth, even gradations of flat tones can not be successfully applied
to photographs without it, and it is therefore indispensable,
especially for retouching skies and covering other large areas.

Before retouching a photograph the draftsman should mix in a saucer a
tint that will match the color of the part that is to be retouched and
should try this tint and note its effect after it has dried and change
it, if necessary, until it matches the color exactly. If he is to
retouch a number of photographs that have the same local color he may
with advantage make up enough of the tint for the entire lot,
thoroughly mixing it and seeing that it is not too thin. In making
this tint he should use only pigments of the best grade, and if he
finds that the Chinese or other white he is using does not photograph
well, or that it does not hold its color, he should discard it at once
and use another brand. Photographs that are to be retouched should be
large enough to permit sufficient reduction to soften the effects of
retouching.

In order to eliminate the lines of junction between two or more
photographs that are joined together to form a panorama some
adjustment or fitting of details by retouching is generally required
before the group is rephotographed to obtain a new print of the whole
on one piece of paper. As it is often desirable to increase the width
of such an illustration the photographer should be instructed to print
the photograph on a strip of paper that is wider than the negative, so
that, if necessary, the retouching may be carried above or below the
new print to add depth to the illustration.

Panoramas may also be drawn from photographs with either pen or brush
in the manner described on pages 68-69.




PART III. PROCESSES OF REPRODUCING ILLUSTRATIONS.




METHODS EMPLOYED.


The preliminary work in producing illustrations includes the
preparation, from originals submitted by authors, of drawings and
other kinds of "copy" in such a way that the copy can be reproduced in
multiple by printing.

Several processes are used for preparing plates for printing
illustrations, and each has its peculiar features of excellence. One
process may render fine details with facility but may fail in
uniformity in large editions; another may be cheap and effective on
the whole but may not reproduce fine details; and still another may
give fine color or tone effects but may be too expensive. Therefore a
knowledge of the varied uses and results and of the cost of the
several processes of reproduction and, on the other hand, of the kinds
of originals that are best suited for reproduction by any one of the
processes is essential to effectiveness and economy in planning,
preparing, and reproducing an illustration.

The following condensed descriptions of processes are intended mainly
to aid in determining the kind of copy that is appropriate for each
process and the kind and quality of reproduction to be expected, so
that only the principal operations or stages in each process are
described. Wood engraving, which was used in making printing plates
for many of the illustrations in the early publications of the
Geological Survey, is described here only to compare that laborious
and "indirect" method of engraving cuts with the more modern kinds of
relief engraving. In 1892 it gave way to photo-engraving.




PHOTO-ENGRAVING.


GENERAL FEATURES

The term "photo-engraving" is applied to processes by which a black
and white line drawing, photograph, or like original is reproduced in
relief on a metal plate from which prints may be made on an ordinary
printing press, in distinction from processes that print from flat or
relatively flat surfaces, such as the lithographic and photogelatin
processes. The photo-engraving processes that are most generally used
are those called "zinc etching" and "half-tone engraving." These
processes depend on the discovery that gelatin or similar organic
material, if treated with potassium or ammonium bichromate and exposed
to the action of light, is made insoluble in water. If a metal plate
coated with bichromatized gelatin or albumen is exposed to light under
a negative the parts acted upon by light become insoluble and those
not acted upon remain unchanged and may be washed away so as to expose
the metal, which is then etched with acid in order to give relief to
the unexposed parts and make of them a printing surface.


ZINC ETCHING.

Zinc etching is adapted to the direct reproduction of a pen and ink
drawing composed of lines, dots, or solid black areas. On the finished
metal plate these lines, dots, and solid areas form the printing
surface, and the spaces between them, which have been etched away,
represent the white or blank parts of the picture. The process is
cheap and is almost universally used for reproducing small drawings
designed for text illustrations. It is also well adapted to the
reproduction of maps and diagrams measuring in print not more than
about 10 by 14 inches. One of the chief advantages of this and of all
other direct (photographic) processes of engraving is that they
reproduce a drawing in facsimile, whereas the "personal equation" must
enter into all engravings made by an indirect method--that is, by
hand--such as wood engraving, wax engraving, and engraving on stone or
copper, which make it necessary to compare every detail of the proof
with every detail of the drawing before the engraving can be approved.
The pen drawing to be reproduced, which should preferably be
considerably larger than the completed engraving, is first
photographed to the proper size or scale on an ordinary negative film.
The film is then stripped from the negative and reversed in order that
the etched plate may print the design as in the original and that the
film may be grouped with other films on one large glass and all
printed at the same time. The negative (whether a single film or
several) is then placed in a specially constructed printing frame in
contact under pressure with a sensitized zinc plate and exposed to
light.

After the zinc plate has been removed from the printing frame (in the
dark room) the plate is rolled with printer's transfer ink, which
resists acid, and placed in a shallow tray containing water, in which
it is rocked for several minutes, and then taken out and rubbed gently
with cotton. The parts of the coating of the plate that were acted on
by light have become insoluble and will therefore be unaffected by the
water, but the parts of the coating not acted on by light and
therefore not hardened will be removed by the washing, which will
expose the metal and leave the parts acted on by light--the
picture--in black lines, dots, etc. The plate is then dusted with
"topping powder," a resinous substance which adheres only to the parts
carrying the ink. The plate is then heated so that the resin and the
ink that remain fuse together and form, when cooled, a resistant
surface which will not be affected by the acid to be used later in
etching the unprotected parts of the plate.

The plate is now ready for a preliminary etching in a fluid consisting
of water and a few drops of nitric acid. It is placed in a tray,
rocked gently for a short time, and then removed, washed well in
running water, drained, and dried with gentle heat. "Dragon's blood,"
a resinous powder that resists the action of acid, is next applied to
the plate, in order to protect the sides of the lines and the dots
from the acid, and the plate is then heated just sufficiently to melt
the powder and units it with the ink. A small quantity of nitric acid
is now added to the etching bath, and the plate is subjected to its
first thorough biting or etching. It is then removed from the bath,
washed under a tap, carefully wiped with a damp rag, and dried with
gentle heat.

The plate is thus treated three or more times until it is etched deep
enough to insure satisfactory printing, and it is then ready for
finishing, which consists of deepening the larger open spaces between
the lines with a routing machine and of cutting away with hand gravers
lines that are improperly connected or that are so close together that
they will not print separately. The routing machine is provided with a
cutting tool mounted on a revolving spindle that projects downward
into the engraved plate, which is securely fastened. The movement of
the arm that holds the cutter is universal and can be controlled with
great precision. The plate is then "proved" that is, a proof is taken
from it on paper and if the proof is satisfactory the plate is nailed
to a block of wood on which it will be "type high" (0.918 inch), for
printing.

Most drawings for zinc etching are made with a pen in black ink and
consist of lines, dots, or masses of black, but drawings may also be
prepared by using some medium that will produce a fine stipple, such
as a black crayon on rough paper or Ross's stipple paper. (See p. 24.)
The drawing should be one and one-half to two or three times as large
as the printed illustration, for it is impossible to obtain a
satisfactory reproduction of a pen and ink drawing without some
reduction. If the drawing has not been reduced the lines appear
heavier in the reproduction than in the drawing, and imperfections
thus become more noticeable; if it has been properly reduced,
imperfections are diminished and the lines and dots become thinner and
finer than those in the drawing. In making a drawing that is to be
reduced the draftsman can also space his lines farther apart and work
out his details more easily.

An author should carefully examine and approve the finished drawings,
which can, of course, be greatly altered, if necessary, before they
are engraved; but similar corrections can not be made on proof sheets
of zinc cuts, which should not be marked for alterations except by
eliminating parts. Minor changes can be made in such a cut by an
expert "finisher," but if the cut is small it is generally cheaper to
correct the drawing and have a new cut made.

Zinc etchings cost about 10 to 25 cents a square inch, the cost being
varied according to a standard scale which is based upon the
ascertained cost of reproduction. The minimum charge for a single cut
is $2.


COPPER ETCHING IN RELIEF.

Copper etching, which produces a line cut in relief, requires the same
kind of copy that is most often marked for zinc etching and is used to
obtain deeper etching and a more permanent cut. It is said to produce
better printing plates than those etched on zinc and is used largely
for reproducing script lettering and other fine work. As copper plates
will hold up longer in printing than zinc, a cut etched on copper may
not need to be electrotyped.

The chemical part of the process is practically the same as that
employed for etching half-tone plates, described under the next
heading.

The cost of etching on copper is considerably greater than the cost of
etching on zinc. This process is not often used in reproducing
illustrations for publications of the Geological Survey.


HALF-TONE ENGRAVING.

The half-tone process is, in name at least, familiar to almost
everyone who has had any connection with the making of books, whether
as author, editor, illustrator, or printer. The invention of a
photomechanical process of reproducing a line drawing to make a metal
plate that could be printed along with type on an ordinary printing
press naturally led to attempts to reproduce similarly a photograph.
It was known that the intermediate shades between white and black in a
photograph--the half tones--can be reproduced on an ordinary printing
press only by breaking them up into dots or lines that will form a
good printing surface and that by their variation in size or density
will give for each shade the effect of a uniform tone. In the
half-tone process this effect is produced by photographing the picture
or object through a screen.

The half-tone screen consists of two plates of glass, on each of which
lines running generally at an angle of 45° to the sides of the plate
have been engraved, cemented together so that the lines cross at
right angles. The lines, which are minute grooves filled with an
opaque black pigment, thus appear as a series of black crossed lines
on a white ground. The screen is placed in the camera in front of the
negative. Screens are made that show from 60 lines to an inch for the
coarser newspaper illustrations to 250 lines or more to the inch for
fine book work. The screens used for magazine illustrations generally
show 120 to 150 lines. Those used for Survey publications show 150 to
175 lines, and for reproducing delicate drawings and photographs of
fossils screens bearing 200 lines to the inch are sometimes specified;
but these finer screens require the use of highly super-coated papers,
some of them made of cheap fiber and not known to be permanent. For a
half tone that is to be printed in the text a 100-line or a 120-line
screen is specified. (See Pl. VI, p. 56.)

The method of etching a half-tone plate does not differ greatly from
that used in zinc etching, and there are several kinds of half-tone
plates, though most of them are etched on copper, not on zinc, those
etched on zinc being used principally for newspaper illustrations. The
half-tone screen is used also in other processes to obtain a negative.

When a half-tone negative hag been made the film is stripped from the
glass plate and reversed, as in the zinc-etching process, though some
half-tone engravers use a mirror box or prism by which the picture is
so disposed on the negative that it does not need stripping and
reversing. A perfectly flat, clean, and highly polished copper plate,
generally large enough to accommodate several such films, is then
coated with a sensitive film according to one of several formulas, all
based on the fact that gelatin or some similar body, if sensitized
with certain chromic salts, becomes hardened and insoluble in water on
exposure to light. This plate is then placed in the printing frame in
contact, under pressure, with the glass negative plate and is exposed
to light in the usual manner. The copper plate is then removed from
the frame in the dark room and made ready for etching.

For etching half-tone plates on copper a saturated solution of
perchloride of iron is used instead of the solution of nitric acid
used for zinc etching. The time of etching ranges from about 5 to 15
minutes, according to the strength of the solution. One etching is
generally sufficient, but it may be necessary to give the plate
another "biting" if it has not been etched deep enough, or to re-etch
it in order to strengthen contrasts. If, for instance, the sky in a
half-tone plate shows too dark or is uneven in tint it can be made
lighter or more even by re-etching. On the other hand, if certain
features on a plate are too light they can be darkened by
burnishing--rubbing the surface with a highly polished steel burnisher
under just sufficient pressure to flatten slightly the fine points
that form the printing surface of the plate. When the plate leaves the
hands of the etcher it is turned over to the finisher, who with a
graver removes spots or any other imperfections that may appear on it.
Sometimes a roulette is used to lighten parts, and other tools are
used for special purposes.

After a plate that shows two or more pictures has been etched and
finished it is divided by sawing them apart. Each one is then put into
a beveling machine, where its edges are trimmed and the usual border
is made, if it is desired. The separate plates are then ready to be
proved and mounted on blocks of wood which make them type high, ready
for printing.

The half-tone process is used almost exclusively for reproducing
photographs and wash drawings, though it will produce a facsimile of
any kind of copy, such as impressions from type, old manuscripts, or
typewriting, but a shade composed of minute black dots will appear
over the entire print and there will be no absolutely whits areas
unless they are produced by routing the plate or cutting out the high
lights. (See p. 74.) The reproduction of an ordinary outdoor
photograph requires very little handwork, except for re-etching,
burnishing, and cutting the borders. In the reproduction of copy that
is made up of separate parts, such as groups of photographs of
specimens that are to appear on a white ground, the half-tone
"tint"--or more properly shade--between and around the several figures
must be removed and numbers must be added. This operation requires two
negatives--one half tone and one line--and produces what is called a
"combination" plate. Therefore the difference in the cost of making a
half-tone cut from a single photograph of a landscape and from a cut
made from "copy" of the same size consisting of a number of small
photographs or drawings, to which numbers or letters are added, is
considerable (about 50 per cent greater) and depends upon the amount
of additional work involved. Routing, when needed, must be done with
extreme care lest the edges of a figure be marred, and this work
requires skill that can be gained only by experience.

Copy for the half-tone process should be as nearly perfect as
possible. Only the best photographs should be selected. Prints on
semimat velox and glossy haloid papers are regarded as the best
photographic copy for reproduction. Every part of the photograph or
drawing should be absolutely clean. If any part that should be pure
white becomes soiled or stained the defects will be reproduced. If a
photograph needs retouching it should be retouched with great care and
just sufficiently to correct defects and to bring out or strengthen
the important details. In many photographs the skies may be "muddy" or
uneven in tone, and this defect can be corrected by the use of an air
brush, the only medium that will produce an almost even tone. As
already stated, half-tone plates can be improved by re-etching and
tooling, but tooling tends to destroy the effects of nature and
produces an artificial appearance in the print. One who is preparing
wash drawings for reproduction by the half-tone process should
remember that brush marks and other inequalities of tone will be
reproduced with as much fidelity as other details. Such drawings
should therefore be made two or three times larger than the engraved
cut in order to subdue all unnatural effects and to soften the general
tones.

Line drawings are not generally suitable copy for the half-tone
process, but it is occasionally desirable to use that process instead
of zinc etching for reproducing a line drawing that has been
inexpertly prepared if the cost of redrawing would more than offset
the difference in cost between zinc etching and the more expensive
half-tone process. In reproducing a pen drawing by half tone the lines
become softened and represent the details and shading only; but the
pen drawing may be further developed by brush work. Examples of this
type of reproduction are Plates V, _A_, VI, _A_, and XV, figure 10,
and other illustrations in Survey Monograph 34.

Vignetting, which consists of a skillful grading off of the edges of a
picture, as well as extensive tooling or hand engraving, is often
employed for artistic effect but should be specified only for
exceptional illustrations. The plates made for the Survey are either
"square trimmed" or the ground tint is entirely omitted or routed
away; they are not usually tooled or vignetted.

Half-tone cuts etched on copper cost 20 to 60 cents a square inch, the
cost being varied according to a standard scale based on the
ascertained cost of reproduction. Those that require a screen finer
than 150 lines cost 25 per cent additional. The minimum charge for a
single cut is $3.

Half tones etched on zinc (100-line screen or coarser) cost 25 per
cent less than those etched on copper.


THREE-COLOR HALF-TONE PROCESS.

The three-color process is practically an adaptation of the half-tone
process to color printing based on the theory that all colors or hues
in nature can be reproduced by combinations of three colors of the
spectrum--red, blue, and yellow. The process differs from the ordinary
half-tone process particularly in the use of color filters in making
the negatives and in the character of screens and diaphragms used.
This process, like all others, is worked somewhat differently in
different establishments. In what is called the indirect method, the
one most commonly used, twelve photographic operations are necessary
to produce one illustration, or the three plates or cuts from which
one illustration is to be reproduced by printing. These twelve
operations produce three chromatic negatives, each representing one
color; three transparencies or positives, made from the chromatic
negatives; three half-tone negatives, made from the positives; and
finally three contact prints, made on sensitized metal plates. In what
is called the direct method the half-tone screen is placed in front of
the photographic plate so that it becomes also a half-tone negative
from which a print is made on a sensitized metal plate. Thus the
photographic operations in the direct method are reduced to six, but
the interference to the passage of light offered by the half-tone
screen and by the prism used to reverse the image on the negative
lengthens the time of exposure.

Unfortunately, no pigments have been found that can reproduce in
purity the colors of the spectrum, and to this fact is due the failure
of the process to reproduce exactly all the colors, tints, and shades
of an original. When a drawing in black on white paper is photographed
only the white paper affects the negative film. The transparent parts
of the developed negative thus represent the black, and the opaque
parts, which have been acted upon by light, represent the whits.
Theoretically, when a chromatic negative is made for the yellow plate
a purple-violet filter cuts out all the yellow and allows the red and
blue rays to affect the plate; when a negative is made for the blue
plate an orange filter similarly cuts out the blue and allows the
yellow and red rays to affect the plate; and when a negative is made
for the red plate a green filter cuts out the red and permits the blue
and yellow rays to affect the plate. These color filters, which are
usually made of transparent stained gelatin, are generally placed in
front of the lens. When printing plates like those used in the
half-tone process have been made from the three negatives and the
plates have been inked with yellow, blue, and red ink, respectively, a
combined impression from them will produce a close approximation of
the subject photographed. The colored inks often used are light
yellow, peacock or prussian blue, and bright, transparent crimson.

The ordinary half-tone screen, which bears lines cut at an angle of
45° to the sides of the plate, is rectangular, but the screens used
for three-color work are made circular in order that they may be
turned in the camera to make the lines intersect at other angles, the
angles being varied to avoid producing an undesirable pattern or a
moire effect. Turning the screen also prevents the exact coincidence
or superposition of the red, blue, and yellow dots, which would
produce black. In other respects the screens do not differ essentially
from those used in ordinary half-tone work.

As special experience is necessary in printing three-color plates the
engraver generally delivers the printed illustrations to the purchaser
instead of the plates, which he furnishes for other kinds of relief
printing.

The copy for this process may consist of anything in color, such as
specimens, objects, paintings, or properly colored photographs. The
process does not usually reproduce all the colors and tints of an
original with equal exactness and is not used by the Survey for work
that demands precise reproduction of color, but it is satisfactory for
reproducing most colored drawings, colored photographs of specimens,
or the specimens themselves if they show individual variations in
color. As the process is entirely photomechanical it gives more
scientific accuracy in detail than chromolithography, in which there
is much hand work, and it is much less expensive. If the colors shown
in proofs are not satisfactory they can be modified.

The four-color process, in which four color plates are used, gives a
closer approximation of true color values than the three-color
process, and at a comparatively small increase of cost. The additional
color used is generally a neutral gray or black.




WAX ENGRAVING (THE CEROTYPE PROCESS).


The wax or cerotype process does not require finished drawings and is
especially suitable for making text illustrations and small maps,
although it may be used also for large work. For this process blue
prints, pencil sketches, old prints, or rough copy of any kind may be
submitted--that is, it is not necessary to furnish carefully prepared
drawings in black ink, as it would be for photo-engraving, for the wax
engraver will reproduce in proper form any illustration in which the
copy and the instructions show what is wanted, just as an experienced
draftsman will make a good drawing from the rough original furnished
by an author. Full and clear instructions should always be given,
however, as to the size of the cut wanted and what it is to show.

In this process a polished copper plate is coated with a film
consisting of beeswax, a whitening medium, and other ingredients, and
the coating, which varies in thickness according to the nature of the
copy, is sensitized as in the ordinary photographic processes. The map
or other design to be engraved is first photographed to publication
size and a contact print is made on the wax coating from the negative.
The lines and other parts of the photographed image are then traced or
cut through the wax to the copper plate with steel tools and
straightened or perfected by the engraver, but the lettering is set in
printer's type, which is pressed into the wax until it also touches
the metal plate. After the work of cutting through the wax has been
completed the larger open spaces between the lines are "built up" by
the addition of wax to give greater depth to the plate, so that the
wax plate thus built up corresponds to an electrotype mold. The plate
is then dusted with powdered graphite and suspended in a solution
containing copper, where by electrolytic action a copper shell is
formed over its surface. When this shell is sufficiently thick it is
removed from the solution and reinforced on the back with metal, and
proofs are taken from it. If the proofs are satisfactory the plate is
blocked type-high.

Wax-engraved plates may be used for printing colored maps or diagrams,
in which variations of tint are produced by various kinds of machine
rulings. The effect of some of the colors thus produced is almost a
"flat" tint, in which a pattern can be detected only by close
scrutiny. Some color work is printed from a wax base plate in
combination with half-tone color plates.

The price of a wax engraving depends entirely on the size of the cut,
the amount of work involved, and the character of the original copy,
but it should not exceed very much the cost of a carefully prepared
pen drawing plus the cost of a zinc etching made from it. Cuts
engraved by the wax process, like zinc and half-tone plates, are
delivered to the purchaser. If colored work is ordered, however, the
printed sheets, not the cuts, are delivered.



WOOD ENGRAVING.


Wood engraving was once the universal method of producing cuts for
illustrations that were designed to be printed on an ordinary press.
It is said to be the oldest of all methods of engraving illustrations.
The engraving is made on a block of boxwood, a very dense, hard wood
of a light-yellow color. The block is cut type-high across the grain,
and the engraving surface is made perfectly smooth by nibbing it with
pumice or other stone. When a cut is to be larger than 3 or 4 inches
square the wood block is made up of pieces securely dovetailed or
joined together to prevent splitting and warping. A woodcut is not
used for printing but is electrotyped and the electrotype is used in
the press.

Originally the smoothed surface of the wood block was coated with
prepared chalk or Chinese whits, and on this coating a finished
drawing was made with a brush and pencil by an illustrator. According
to more recent practice the surface of the wood is covered with a
sensitized coating, on which the drawing or design to be engraved is
photographed. The engraver then, with various kinds of gravers and
other tools, cuts out the parts of the picture that are to be
represented by white paper and leaves the lines, dots, and black areas
as a printing surface, thus translating the shades and tints of the
picture into a system of lines and dots which exactly duplicate, in
effect, the details and tones of the original design. In order to
produce a line effect of an area in which the tone is intermediate
between whits and black the engraver must space his lines so that
one-half the area will remain as printing surface and the other half
as white spaces, and he must give character and direction to his
lines, so that, if he is skillful, he can reproduce not only the
delicate tones but the texture and details of the original picture.
Many wood engravers became noted for their artistic rendering of
magazine illustrations, of famous paintings, and of other works of
art.

The Survey began to abandon this method of engraving in 1884, when the
Sixth Annual Report was in press, substituting for it the cheaper
photomechanical processes, zinc etching and half-tone engraving, and
entirely abandoned its use in 1892.

Many good examples of wood engraving may be found in the early
monographs and annual reports of the Geological Survey. Monograph 2
contains numerous examples.



PHOTOGELATIN PROCESSES.


Bichromatized gelatin is used in several photomechanical processes of
reproducing illustrations, but in the photogelatin processes the
gelatin not only receives the image by exposure to light through a
negative but becomes a printing surface on a plate from which prints
are made somewhat as in lithography. The several photogelatin
processes are much the same as the original collotype process and are
best known by the names collotype, heliotype, albertype, artotype, and
the German name lichtdruck.

In working these processes a thick plate of glass, after certain
preliminary treatment, is coated with sensitized gelatin. The plate is
then placed in a drying room or oven having a temperature of 120° F.,
baked until it is thoroughly dry, and allowed to cool gradually. The
subject to be reproduced is then photographed in the usual manner, and
unless a prism or mirror box has been used the negative is stripped
and reversed in order to make the print reproduce the original in
proper position. From the negative a contact print is made on the
gelatin-coated plate, the parts or molecules of gelatin being hardened
in proportion to the amount of light that affects them. After the
contact print has been made the gelatin plate is thoroughly washed in
cold water, in order to dissolve and wash out the bichromate and stop
any further action of light on the plate, and is then thoroughly
dried. Before prints are made from the gelatin-coated plate water is
flowed on it and penetrates different parts of the gelatin according
to their hardness. The darkest parts of the picture will correspond to
the hardest and densest parts of the gelatin, which will not absorb
water; the lighter parts will take up more water. The surface water
is then removed with a rubber straight edge and an absorbent roller
and the plate is ready for inking. The ink, being greasy, has no
affinity for water, and when it is rolled over the plate it adheres
only to the dry parts of the gelatin, and in the press is carried to
the paper in all the lights and shades of the illustration. The plate
is kept moist in printing.

The paper used for printing from photogelatin plates must be free from
chemicals that will affect the gelatin. A nearly pure rag paper is
generally used.

The photogelatin process is well adapted to the reproduction of
paleontologic drawings, wash drawings, photographs, photomicrographs,
works of art, old manuscripts--in fact, any kind of subject in which
the reproduction of delicate lights and shades is essential. If
properly manipulated it has distinct advantages over the half-tone
process in that it can reproduce details and light and shade without
showing the effect of a screen and without the use of coated paper.
Excellent reproductions by the heliotype process are also made in
color by first printing the design in a neutral tone and superposing
appropriate transparent colors on this print, somewhat as in
chromolithography, so that the colors softly blend with the shaded
groundwork.

Reproductions made by the photogelatin process are more expensive than
those made by the half-tone process, for the prints are generally made
on better paper and are printed with greater care. They give no screen
effect and are perhaps unrivaled by prints obtained by any other
process except photogravure, in which the image is printed from a
metal plate that has been sensitized, exposed under a reversed
negative, and etched.

Changes can not be made on photogelatin plates except by making over
the corrected parts. All retouching must be done on the originals or
on the negatives made from then.




LITHOGRAPHY.


ORIGINAL PROCESS.

The general term "lithography" is sometimes used to indicate not only
the original process so named, said to have been invented by
Senefelder, but chromolithography, photolithography, and engraving on
stone, as well as engraving on copper as a means of supplying matter
to be transferred to and printed from a lithographic stone.

Senefelder discovered that limestone will absorb either grease or
Water, and that neither one will penetrate a part of the surface
previously affected by the other. He found that if a design is drawn
on limestone with a greasy crayon and the stone afterward properly
prepared with a solution of nitric acid and gum, greasy ink will
adhere only to the parts that are covered with the crayon, and that
the stone will give off an impression of the design.

Lithographic stone is described as a fine, compact, homogeneous
limestone, which may be either a pure carbonate of lime or
dolomitic--that is, it may contain magnesium. Although limestone is
one of the most common rocks, limestone of a quality suitable for use
in lithography is found at only a few localities.[11] There are two
general classes of lithographic stone, known to the trade as "blue" or
hard stone and "yellow" or soft stone. The blue stone is adapted for
engraving and to the better grade of fine-line printing; the yellow
stone is rated as somewhat inferior.

[Footnote 11: Kubel, S. J., Lithographic stone: U. S. Geol. Survey
Mineral Resources, 1900, pp. 869-873, 1901.]

In the original process, which may here be termed plain lithography,
two methods are employed in putting on stone the design to be
reproduced. In one the subject or picture to be reproduced is drawn on
the printing stone either with a lithographic crayon or with a pen
dipped in lithographic ink or "tusche," which is oily or fatty, like
the crayon. In the other method the drawing is made on transfer paper
and transferred to the stone. In drawing on stone it is necessary to
reverse the design, so that all lettering must be drawn backward. In
doing this the artist often uses a mirror to aid him. If the drawing
is made on transfer paper the design and the lettering are copied as
in the original--not reversed.

Before a drawing is made on stone a stone of the quality suited to the
particular design in hand is selected. The stone is then ground and
polished, and if the drawing is to be made with crayon it is "grained"
according to the special requirements of the subject. If the drawing
is to be made with a pen and is to consist of "line work" the stone is
polished. The first step is to obtain on the stone an outline or
"faint" of the design. There are several ways to do this. By one
method a tracing of the design is made, a sheet of thin paper covered
with red chalk is laid face downward on the stone, the tracing is laid
face downward over it, and the design is again traced in red-chalk
lines on the stone. The method described is simple, but there are
others that are more complicated and that are particularly applicable
to the reproduction of photographs and other illustrations. Crayon
work is often used in combination with pen and ink, stipple, and brush
work. This method of drawing on stone is used also for preparing color
stones in the process of chromolithography, in which there are many
added details of manipulation. After the drawing has been made on the
stone or transferred to it the stone is "gummed"--that is, it is
covered with a solution of gum arabic and nitric acid--and dried. The
stone is then dampened with water and carefully rolled with
lithographic ink, which adheres to the pen or crayon work and is
repelled elsewhere. It is then "rubbed" over with powdered rosin and
talcum, which adheres to the ink and further protects the drawing from
the effects of the etching fluid, which is next to be applied to the
stone. This fluid consists of a 10 per cent solution of gum arabic to
which 2 to 7 per cent of nitric acid has been added, the degree of
acidity being varied according to the subject and the hardness of the
stone. The fluid is applied with a brush or sponge and is left on the
stone just long enough to decompose slightly the carbonate of lime on
its surface and, after washing, to leave the design or drawing in very
slight relief. The stone is again gummed and dried, and the design is
"washed out" or brought out by removing the surface gum with a wet
sponge and applying to the stone a rag sprinkled with turpentine and
charged with printing ink. These operations wash away the tusche and
the crayon that have been decomposed by the acid and expose the design
faintly in white at first, but it gradually grows darker as it becomes
charged with printing ink from the rag. The stone is next "rolled up"
or inked. The slightly moistened surface repels the ink and the design
takes it up, so that when the stone is run through the press the
design is carried to the paper.

Lithographic prints from stones prepared in this way are made on a
flat-bed press. The stone is carried forward to print and on its
return is dampened and inked, an operation slower than that of rotary
printing.

Corrections and changes are made on the stone by carefully scraping or
polishing away the parts to be corrected and making the changes with a
crayon or pen, but the design can not ordinarily be corrected twice in
the same place, as the scraping or polishing removes a part of the
surface of the stone and thus lessens the pressure at that place, and
the impression there may be imperfect or may completely fail.

This form of lithography is seldom used for Survey illustrations but
was formerly much used and is well adapted to the reproduction of
drawings of fossils, particularly of remains of dinosaurs and other
types of large extinct animals. Examples may be seen in Monographs 8
and 10 and in other early reports of the Geological Survey. The
drawings for these illustrations were made directly on stone.

A drawing made on one stone may be transferred in duplicate or in any
desired number to another stone, or to a properly grained sheet of
zinc and aluminum, from which impressions may be printed on a
lithographic press. Both these metals are also used for lithographic
printing on rotary presses, the zinc or aluminum plate being bent and
secured around a cylinder which rotates continuously in one direction.
As one impression is made at each revolution of the cylinder the
printing is rapid; but the best printing from a metal plate is
inferior to the best printing from a lithographic stone.


PHOTOLITHOGRAPHY.

Photolithography, like other lithographic processes, has been improved
greatly during the last few years--not particularly in results but in
methods--by the introduction of metal plates, the rubber blanket
offset, the Ben Day films, and many mechanical and chemical devices,
so that a brief description of it will not explain the process except
in a most general way. As photolithography is a direct process and is
relatively cheap it is the one most used for reproducing large maps
and other line drawings that have been carefully prepared. Zinc and
aluminum plates are now much used in photolithography, for a direct
contact photographic print can be made on them, they can be printed
flat or bent for use on a rotary press, and they can be stored for
future use more economically than stones.

There are two somewhat distinct methods of producing photolithographs.
In both the ordinary photographic methods are used, but it is often
necessary to "cut" or trace parts of the negative in order to open up
lines and other features that are not sharp or well defined, so that
the negative will print them sharp and clear. If the copy to be
reproduced shows three colors, three negatives are made, one for each
color, and the parts to be shown by each are preserved by "opaquing"
or painting out all other parts. By the older method the negative thus
perfected is placed in a printing frame in contact, under pressure,
with sensitized transfer paper and is exposed to light. The printing
frame is then carried to the dark room and the paper is removed from
the frame and its surface covered with transfer ink. The paper is then
laid face upward on water and soaked for several minutes, after which
it is placed in the same position upon a slab of stone or metal and
thoroughly washed with water. This washing removes the ink and the
sensitive film from the parts that were unaffected by the action of
light (the parts corresponding to the white paper in the design), but
the ink still adheres to the lines of the design in the precise
sharpness and clearness of the negative. The design is now ready to be
transferred to the printing stone or zinc plate. The sheet is again
slightly dampened between moist blotters and laid face downward in its
correct position on a prepared stone or zinc plate, which is then
pulled through a press under heavy pressure. The paper is then removed
from the stone or plate, to which it has carried the design. From this
point the gumming, etching, and other operations are practically the
same as those used in ordinary lithography.

The bichromate-gelatin transfer process described above has been
replaced in the Survey by a more satisfactory one, which insures
absolute scale and reproduces the finest line drawings perfectly
without thickening the lines or without distortion. In this process,
which is known as the planographic process, a photographic negative of
the "copy" is placed in a vacuum printing frame in contact with a zinc
or aluminum plate that has been sensitized with a bichromate-albumen
solution and exposed in front of an arc lamp. After proper exposure
the plate is removed from the frame, inked over, and placed under
water. The parts not hardened by the action of light (the unexposed
parts) are then rubbed away with cotton, and the plate is chemically
etched, gummed over, and dried. The plate is then ready to be printed
from in a lithographic press. If a large map is to be reproduced it is
photographed in parts, and contact prints are made on zinc plates.
From these plates transfers are pulled and the parts are assembled and
laid down in proper position on a stone or an aluminum plate, which is
then prepared for printing.

A drawing that is to be reproduced by photolithography should be made
on pure-white paper in lines, dots, or black masses with black
waterproof ink. It should be one and one-half to two or three times
the size of the finished print.

Photolithography is particularly adapted to the reproduction of maps,
plans, and other large drawings. Within certain limitations, lines may
be changed and details may be added after proofs have been submitted.
The process is ordinarily used for reproducing illustrations in one
color (black), but it is used also for printing in more than one
color, generally over a black outline base, each color being printed
from a separate stone, as in chromolithography.


OFFSET PRINTING.

In the offset process the design is "offset" from a lithographic plate
or stone to a rubber blanket on a cylinder, from which it is printed.
By thus obtaining an impression from an elastic surface the finest
details can be printed on rough, uncoated paper, which can not be used
in other processes, which can be folded without danger of breaking,
and which is more durable than coated paper. Plates II, III, IV, VII,
and VIII in this pamphlet were printed by this process.


CHROMOLITHOGRAPHY.

The chromolithographic process, by which illustrations are printed in
color from stone, is used in Survey publications principally for
reproducing geologic maps, but it is sometimes used for reproducing
colored drawings of specimens.

There are several kinds of color printing from stones. One produces a
picture by superimposing colors that combine and overlap without
definite outlines and thus reproduce the softly blended colors of the
original. Another reproduces the original by printing colors within
definite outlines on a "base" which has been previously printed in
black. The first kind is used by the Survey for reproducing colored
drawings of specimens. The second is followed in reproducing geologic
maps.

As each color must be printed from a separate stone and properly
fitted with respect to the others a tracing from the original is made
of the precise outlines of each color; or, if the design is to be
reduced, a tracing is made over a properly reduced photographic print.
This tracing can be made on specially prepared tracing paper or on a
sheet of transparent gelatin or celluloid, which is laid over the copy
and on which all the outlines and overlaps of the various colors are
scratched with a steel point. The scratches thus made on the celluloid
are filled with red chalk or like substance, and rubbed in with
cotton, and by reversing the sheet and rubbing it the chalk lines are
deposited on as many stones as are needed to produce the colors of the
original design, each stone bearing all the outlines of the design.
Sometimes all the outlines are engraved on what is called a key stone
and an impression from it is laid down on each of the color stones.
The parts on each stone that are to have one color are then inked in
or engraved, and at the same time guide marks are indicated, so that
in the composite print from the stones each color will fit its proper
place. This fitting is called "register" and is an important part of
printing, for each stone must be adjusted to a nicety while on the
press in order to make each impression fit the others exactly. The
process was originally manipulated entirely by hand, but photography
has now replaced much of the handwork and has given rise to several
methods by which the same kinds of subjects are reproduced in
radically different ways. Tints are sometimes produced by the
half-tone and other screens and by machine ruling, and printer's type
is used almost exclusively for titles and other matter that was
formerly engraved or drawn on the stone.

In reproducing a geologic map the base may be engraved on stone or on
copper or it may be photo-lithographed. By either process the map may
be transferred to the printing stone. The color stones for geologic
maps are prepared by hand, but the geologic patterns, which are
printed in colors, are engraved separately on plates, from which
impressions are pulled when needed and transferred to their proper
places on the printing stones in the shapes required according to the
"key" design. The lighter, more transparent colors are generally
printed first, and often twelve or more colors and many distinctive
patterns are used to produce a geologic map. When proofs of such a map
are pulled each stone must be taken up and carefully adjusted on the
press, so that the work of proving maps that are printed from a
considerable number of color stones is laborious and expensive.
It is therefore customary to approve first combined proofs
conditionally--that is, subject to the corrections and changes
indicated on the proofs--and to hold the lithographer responsible for
any failure to make the corrections.

This process is the most expensive one used for reproducing
illustrations. Changes may be indicated on proofs, but changes can not
be made on a stone twice in the same place without danger of affecting
the printing or making it necessary to retransfer the parts affected.
All changes are expensive because a slight modification at one point
may involve corresponding changes on a number of stones, each of which
must be taken up, corrected, and proved to insure the exact
coincidence of the parts affected. It is often less expensive to
retransfer the entire job than to make extensive changes on the
original stones.


ENGRAVING ON STONE AND ON COPPER.

Engraving on stone is distinctly lithographic, but engraving on copper
is sometimes included among lithographic processes because the work
produced by it is usually printed from stone and thus becomes
lithographic. In other respects engraving on copper is not a
lithographic process. Roughly prepared maps and any rough line copy
that is accurate in statement and clear as to intent are appropriate
for both methods of engraving, but drawings that are expertly prepared
are more suitable for reproduction by photolithography. In engraving
on stone the lines of a design are scratched on the blackened surface
of a stone with a steel-pointed tool; in engraving on copper the lines
are cut with a graver on a sheet or plate of copper, the matter to be
engraved being first shown on the plate by what is called the
photo-tracing process, which was devised in the Geological Survey.
There is, however, no great or essential difference in the printed
results of the two processes, but most lithographers employ only stone
engravers.

A stone on which a design is to be engraved is ground and polished
according to the kind of work to be engraved, is coated with a thin
solution of gum arable and allowed to dry, and is then washed until
the superficial gum is removed while the surface pores remain filled.
As the lines made by the engraver must be visible the stone is
blackened with a pigment composed of lampblack and gum or is covered
evenly with red chalk or Venetian red. It is then ready to receive the
design to be engraved.

If the design is a map which is to show culture, streams, and surface
contours, and each of these sets of features is to be printed in a
separate color, impressions of the work to be engraved must be placed
on three stones. One method of doing this is to make a scratch tracing
of the original drawing on a sheet of transparent gelatin or celluloid
in the manner employed in chromolithography, except that a dry
pigment, generally chrome-yellow, is used to fill the scratch lines
instead of red chalk or Venetian red. From this tracing a "faint" or
imprint of all the details of the three separate features of the map
is made on each of the three stones, and the engraver then cuts on
each stone only the lines and other features, including ample register
marks, that are to be printed in one color, the imprint made from the
tracing making it possible to engrave each set of features in its
exact position relative to the other two. By another method the matter
to be engraved is photographed directly on the stone.

The engraving is done with a steel needle inserted in a small wooden
cylinder, an instrument resembling an ordinary lead pencil. The size
and shape of the needles used are varied according to the requirements
of the matter to be engraved. With this instrument the lines and
lettering are lightly scratched into the stone through the dark
coating and show as light lines. The points of some of the needles are
fine; those of others are V-shaped; and some have spoon-shaped points,
for use in thickening lines and shading letters. All features are
engraved in reverse.

After the engraving is completed the stones are prepared for printing
by wiping off all the superficial color and filling the engraved lines
with a greasy ink--generally a thin printing ink--which is rubbed into
the lines with a soft rag. Impressions are then pulled on transfer
paper and transferred to three printing stones for use in printing the
three colors, the register marks enabling the pressman to fit each
color exactly in its proper place.

In all lithographic processes the titles and other marginal lettering
can be and usually are transferred from type impressions to the
printing stones. It is therefore unnecessary to letter such matter
carefully on an original drawing that is made for lithographic
reproduction, for appropriate faces of type will give better printed
results than hand lettering.

Corrections can not be made on a stone or copper engraving as readily
as on a drawing. If a stone engraver makes an error or if a change is
required after his engraving is finished, the parts to be corrected
must be scraped off and a new ground laid before the correction can be
made. Sometimes he will engrave the parts corrected on another part of
the original stone and transfer it to the printing stone. Corrections
are made on copper plates by "hammering up" the plate from beneath,
polishing off a new surface, and reengraving the part to be corrected.




APPENDIX.


The matter given in this appendix is much used in making geologic maps
and other illustrations. The Greek alphabet and the groups of signs
presented are given chiefly to show the correct formation of each
letter and sign.




MISCELLANEOUS TABLES.


_Length of 1° of longitude measured along given parallels from the
Equator to the poles._

[From U. S. Coast and Geodetic Survey Report for 1884, Appendix 6.]

  Parallel of   Statute | Parallel of   Statute | Parallel of   Statute
   latitude.     miles. |  latitude.     miles. |  latitude.     miles.
  ----------------------+-----------------------+----------------------
        0       69.172  |      31       59.365  |      61       33.623
        1       69.162  |      32       58.716  |      62       32.560
        2       69.130  |      33       58.071  |      63       31.488
        3       69.078  |      34       67.407  |      64       30.406
        4       69.005  |      35       66.725  |      65       29.315
        5       68.911  |      36       66.027  |      66       28.215
        6       68.795  |      37       65.311  |      67       27.106
        7       68.660  |      38       64.679  |      68       26.988
        8       68.504  |      39       63.829  |      69       24.862
        9       68.326  |      40       53.063  |      70       23.729
       10       68.129  |      41       62.281  |      71       22.589
       11       67.910  |      42       51.483  |      72       21.441
       12       67.670  |      43       60.669  |      73       20.287
       13       67.410  |      44       49.840  |      74       19.127
       14       67.131  |      45       48.995  |      75       17.960
       15       66.830  |      46       48.136  |      76       16.788
       16       66.510  |      47       47.261  |      77       15.611
       17       66.169  |      48       46.372  |      78       14.428
       18       65.808  |      49       45.469  |      79       13.242
       19       65.427  |      50       44.652  |      80       12.051
       20       65.026  |      51       43.621  |      81       10.857
       21       64.606  |      52       42.676  |      82        9.659
       22       64.166  |      53       41.719  |      83        8.458
       23       63.706  |      54       40.749  |      84        7.256
       24       63.228  |      55       39.766  |      85        6.049
       25       62.729  |      56       38.771  |      86        4.842
       26       62.212  |      57       37.764  |      87        3.632
       27       61.676  |      58       36.745  |      88        2.422
       28       61.122  |      59       35.716  |      89        1.211
       29       60.548  |      60       34.674  |      90         .000
       30       59.956  |                       |

_Length of 1° of latitude measured along a meridian at given
parallels._ [Parallel given is in center of the degree whose length is
stated.]

  Parallel of    Statute
   latitude.      miles.
  ----------------------
       0         68.704
      10         68.725
      20         68.786
      30         68.879
      40         68.993
      50         69.115
      60         69.230
      70         69.324
      80         69.386
      90         69.407


Metric system and equivalents.

[The units of linear measure most commonly used are millimeters (mm.),
centimeters (cm.), decimeters (dm.), meters (m.), and kilometers
(km.), 1 m. = 10 dm.; 1 dm. = 10 cm.; 1 cm. = 10 mm.; 1 km. = 1,000
meters = 0.62137 mile; 1 m. = 39.37 inches = 3.280833 feet.]


    Meters. |   Inches.   || Meters. |    Feet.  || Kilometers. |   Miles.
  ----------+-------------++---------+-----------++-------------+---------
      1     |    39.37    ||    1    |  3.280633 ||     1       | 0.62137
      2     |    78.74    ||    2    |  6.561667 ||     2       | 1.24274
      3     |   118.11    ||    3    |  9.842500 ||     3       | 1.86411
      4     |   157.48    ||    4    | 13.123333 ||     4       | 2.48548
      5     |   196.85    ||    5    | 16.404166 ||     5       | 3.10685
      6     |   236.22    ||    6    | 19.685000 ||     6       | 3.72822
      7     |   275.59    ||    7    | 22.965833 ||     7       | 4.34959
      8     |   314.96    ||    8    | 26.246666 ||     8       | 4.97096
      9     |   354.33    ||    9    | 29.527500 ||     9       | 5.59233

    Inches. | Centimeters.||   Feet. |  Meters.  ||   Miles.  | Kilometers.
  ----------+-------------++---------+-----------++-----------+------------
      1     |     2.54    ||     1   |  0.304801 ||     1     |   1.60935
      2     |     5.08    ||     2   |  0.609601 ||     2     |   3.21869
      3     |     7.62    ||     3   |  0.914402 ||     3     |   4.82804
      4     |    10.16    ||     4   |  1.219202 ||     4     |   6.43739
      5     |    12.70    ||     5   |  1.524003 ||     5     |   8.04674
      6     |    15.24    ||     6   |  1.828804 ||     6     |   9.65606
      7     |    17.78    ||     7   |  2.133604 ||     7     |  11.26543
      8     |    20.32    ||     8   |  2.438405 ||     8     |  12.87478
      9     |    22.86    ||     9   |  2.743205 ||     9     |  14.48412

The "vara," used in Texas, is equivalent to 33-1/3 inches and is
computed as representing 2.78 feet.


_Geologic eras, periods, systems, epochs, and series._


    Era.         Period or system.     Epoch or series.

               {                     { Recent.
               { Quaternary.         { Pleistocene (replaces "Glacial").
  Cenozoic.    {
               {                     { Pliocene.
               { Tertiary.           { Miocene.
               {                     { Oligocene.
               {                     { Eocene.

               {                     { Upper (Gulf may be used
               {                     {   provincially).
               { Cretaceous.         { Lower (Comanche and Shasta may be
               {                     {   used provincially).
               {
               {                     { Upper.
  Mesozoic.    { Jurassic.           { Middle.
               {                     { Lower.
               {
               {                     { Upper.
               { Triassic.           { Middle.
               {                     { Lower.

               {                     { Permian.
               {                     { Pennsylvanian (replaces "Upper
               { Carboniferous.      {   Carboniferous").
               {                     { Mississippian (replaces "Lower
               {                     {   Carboniferous").
               {
               {                     { Upper.
               { Devonian.           { Middle.
               {                     { Lower.
               {
  Paleozoic.   { Silurian.
               {
               {                     { Upper (Cincinnatian may be used
               {                     {   provincially).
               { Ordovician.         { Middle (Mohawkian may be used
               {                     {   provincially).
               {                     { Lower.
               {
               {                     { Saratogan (or Upper Cambrian).
               { Cambrian.           { Acadian (or Middle Cambrian).
               {                     { Waucoban (or Lower Cambrian).

               { Algonkian. }pre-Cambrian.
  Proterozoic. { Archean.   }


_Chemical elements and symbols._

  Element.   Symbol.    Element.     Symbol.   Element.         Symbol.

  Aluminum     Al       Holmium        Ho        Rhodium          Rh
  Antimony     Sb       Hydrogen       H         Rubidium         Rb
  Argon        Al       Indium         In        Ruthenium        Ru
  Arsenic      As       Iodine         I         Samarium         Sa
  Barium       Ba       Iridium        Ir        Scandium         Sc
  Bismuth      Bi       Iron           Fe        Selenium         Se
  Boron        B        Krypton        Kr        Silicon          Si
  Bromine      Br       Lanthanum      La        Silver           Ag
  Cadmium      Cd       Lead           Pb        Sodium           Na
  Cesium       Cs       Lithium        Li        Strontium        Sr
  Calcium      Ca       Lutecium       Lu        Sulphur          S
  Carbon       C        Magnesium      Mg        Tantalum         Ta
  Cerium       Ce       Manganese      Mn        Tellurium        Te
  Chlorine     Cl       Mercury        Hg        Terbium          Tb
  Chromium     Cr       Molybdenum     Mo        Thallium         Tl
  Cobalt       Co       Neodymium      Nd        Thorium          Th
  Columbium    C        Neon           Ne        Thulium          Tm
  Copper       Cu       Nickel         Ni        Tin              Sn
  Dysprosium   Dy       Niton          Nt        Titanium         Ti
  Erbium       Er       Nitrogen       N         Tungsten         W
  Europium     Eu       Osmium         Os        Uranium          U
  Fluorine     F        Oxygen         O         Vanadium         V
  Gadolinium   Gd       Palladium      Pd        Xenon            Xe
  Gallium      Ga       Phosphorus     P         Ytterbium
  Germanium    Ge       Platinum       Pt         (Neoytterbium)  Yb
  Glucinum     Gl       Potassium      K         Yttrium          Y
  Gold         Au       Praseodymium   Pr        Zinc             Zn
  Helium       He       Radium         Ra        Zirconium        Zr


_Greek alphabet._

  Caps.        Lower-case.  Greek name.  English sound.
  [Greek: A]   [Greek: a]   Alpha.       A.
  [Greek: B]   [Greek: b]   Beta.        B.
  [Greek: G]   [Greek: g]   Gamma.       G.
  [Greek: D]   [Greek: d]   Delta.       D.
  [Greek: E]   [Greek: e]   Epsilon.     E short.
  [Greek: Z]   [Greek: z]   Zeta.        Z.
  [Greek: H]   [Greek: h]   Eta.         E long.
  [Greek: Th]  [Greek: th]  Theta.       Th.
  [Greek: I]   [Greek: i]   Iota.        I.
  [Greek: K]   [Greek: k]   Kappa.       K.
  [Greek: L]   [Greek: l]   Lambda.      L.
  [Greek: M]   [Greek: m]   Mu.          M.
  [Greek: N]   [Greek: n]   Nu.          N.
  [Greek: X]   [Greek: x]   Xi.          X.
  [Greek: O]   [Greek: o]   Omicron.     O short.
  [Greek: P]   [Greek: p]   Pi.          P.
  [Greek: R]   [Greek: r]   Rho.         R.
  [Greek: S]   [Greek: s]   Sigma.       S.
  [Greek: T]   [Greek: t]   Tau.         T.
  [Greek: U]   [Greek: u]   Upsilon.     U.
  [Greek: F]   [Greek: f]   Phi.         F.
  [Greek: Ch]  [Greek: ch]  Chi.         Ch.
  [Greek: Ps]  [Greek: ps]  Psi.         Ps.
  [Greek: Om]  [Greek: om]  Omega.       O long.


_Roman numerals._

     I     1   |     IX     9   |    LXX    70   |      D   500
    II     2   |      X    10   |   LXXX    80   |     DC   600
   III     3   |    XIX    19   |     XC    90   |    DCC   700
    IV     4   |     XX    20   |      C   100   |   DCCC   800
     V     5   |    XXX    30   |     CL   150   |     CM   900
    VI     6   |     XL    40   |     CC   200   |      M  1000
   VII     7   |      L    50   |    CCC   300   |     MD  1500
  VIII     8   |     LX    60   |     CD   400   |    MCM  1900


Mathematical signs.

  +   plus.                 ~   difference
  -   minus.                    integration.
  ×   multiplied by.            equivalence.
  ÷   divided by.           :   ratio.
  =   equality.                 geometrical proportion.
  ±   plus or minus.        -:   difference, excess.
      square.                  therefore.
      rectangle.               because.
      triangle.                 infinity.
      circle.                  varies as.
      angle.                    radical.
      right angle.          °   degree.
    or > greater than.      '   minute.
    or < less than.         "   second.
      perpendicular.




NAMES OF ROCKS.


The following list was prepared in the geologic branch for the use of
geologic draftsmen to enable them to select appropriate symbols for
rocks that may be referred to in preliminary drawings by name only.
For sedimentary rocks dots and circles, parallel lines, and broken or
dotted lines are used; for metamorphic rocks short dashes arranged
without definite patterns; and for igneous rocks patterns composed of
short dashes, triangles, rhombs, crosses, and cross lines. All these
patterns are shown in Plate III.


_Sedimentary material._

[Including residual, detrital, eolian, glacial, organic, and
chemically precipitated material.]


  Agglomerate.                        Ironstone (also igneous).
  Alabaster.                          Itacolumite.
  Alluvium.                           Kame.
  Alum shale.                         Kaolin.
  Anhydrite.                          Laterite.
  Apron (alluvial).                   Lignite.
  Argillite.                          Limestone.
  Arkose.                             Limonite.
  Asphalt.                            Loess.
  Bench gravel.                       Marble (also metamorphic).
  Bentonite.                          Marl.
  Boulder clay.                       Metaxite.
  Brea.                               Morainal deposit.
  Breccia.                            Mudstone.
  Brownstone.                         Novaculite.
  Burrstone.                          Peat.
  Calcarenite.                        Pelite.
  Calc sinter.                        Phosphate rock.
  Caliche.                            Phosphorite.
  Catlinite.                          Phthanite.
  Chalk.                              Psammites.
  Chert.                              Psephites.
  Clay.                               Puddingstone.
  Coal.                               Pyroclastic material.
  Conglomerate.                       Quartzite (also metamorphic).
  Coprolite.                          Reddle.
  Coquina.                            Rock salt.
  Detritus.                           Rock stream.
  Diatomaceous earth.                 Rubble.
  Diluvium.                           Salt.
  Dolomite.                           Sand.
  Drift.                              Sandstone.
  Fan (alluvial).                     Selenite.
  Fanglomerate.                       Shale.
  Flagstone.                          Silt.
  Flint.                              Slate (also metamorphic).
  Freestone.                          Soil.
  Fuller's earth.                     Stalactite.
  Geyserite.                          Stalagmite.
  Gravel.                             Talc.
  Graywacke.                          Talus.
  Greensand.                          Till.
  Grit.                               Travertine.
  Gumbo.                              Tripoli.
  Gypsum.                             Tufa (=chemically deposited lime).
  Hardpan.                            Tuff (=igneous fragments).
  Hematite.                           Wacke.
  Infusorial earth.                   Wash.


_Metamorphic material._

  Adinole.                           Hornstone.
  Amphibolite.                       Itabirite.
  Andalusite schist (?).             Kinzigite.
  Apo (rhyolite), etc.               Knotenschiefer.
  Argillite.                         Knotty schists.
  Augen gneiss (also igneous).       Luxulianite (igneous?).
  Biotite schist.                    Marble.
  Calc schist.                       Meta (diabase), etc.
  Cataclastic.                       Mica schist.
  Chlorite schist                    Mylonite.
  Clay slate.                        Ophicalcite.
  Damourite schist.                  Ottrelite schist.
  Desmosite.                         Phyllite.
  Dynamometamorphic rock.            Porcelanite.
  Eclogite.                          Protogene.
  Epidosite.                         Pyroschists.
  Erlan.                             Quartz.
  Erlanfels.                         Quartzite.
  Eulysite.                          Quartz schist.
  Fibrolite schist                   Schist.
  Garnet rock.                       Sericite schist, etc.
  Garnet schist.                     Serpentine.
  Gneiss.                            Slate.
  Granite gneiss.                    Soapstone.
  Graywacke (?).                     Sodalite.
  Green schists.                     Spilosite.
  Greenstone (also igneous).         Steatite.
  Greisen.                           Talc schist.
  Halleflinta.                       Topazfels.
  Hornblende schist                  Topaz rock.
  Hornfels.                          Zobtenite.


_Igneous material._

  Absarokite.                        Dolerite.
  Abyssal.                           Dunite.
  Adamellite.                        Durbachite.
  Adendiorite.                       Effusive rock.
  Ailsyte.                           Ekerite.
  Åkerite.                           Elvan.
  Alaskite.                          Enstatite.
  Albitlte.                          Eruptive rock.
  Allivalite.                        Essexite.
  Allochetite.                       Estrellite.
  Alnölte.                           Eulysite.
  Alsbachite.                        Extrusive rock.
  Ambonite.                          Farrisite.
  Amherstite.                        Felsite.
  Analcitite.                        Felsophyre.
  Andesite.                          Fergusite.
  Anorthosite.                       Fortunite.
  Aphanitite.                        Fourchite.
  Aplite.                            Foyaite.
  Arkite.                            Gabbro.
  Atatschite.                        Gauteite.
  Augen gneiss (also metamorphic).   Garewaite.
  Augitite.                          Glumarrite.
  Avezacite.                         Gladkaite.
  Banakite.                          Granite.
  Banatite.                          Granitite.
  Bandaite.                          Granitoid.
  Basalt.                            Granodiorite.
  Basanite.                          Granophyre.
  Beerbachite.                       Greenstone (also metamorphic).
  Bekinkinite.                       Greisen (?).
  Bombs.                             Grorudite.
  Borolanite.                        Harrisite.
  Bostonite.                         Harzburgite.
  Camptonite.                        Haüynophyre.
  Carmeloite.                        Hawaiite.
  Cascadite.                         Hedrumite.
  Chibinite.                         Heumite.
  Ciminite.                          Holyokeite.
  Comendite.                         Hornblendite.
  Complementary rocks.               Hypabyssal rock.
  Coppaelite.                        Hyperite.
  Cortlandite.                       Hypersthenite.
  Cromaltite.                        Ijolite.
  Cumberlandite.                     Intrusive rock.
  Cuselite.                          Irruptive (=Intrusive) rock.
  Dacite.                            Isenite.
  Dellenite.                         Jacupirangite.
  Diabase.                           Jumillite.
  Diallagite.                        Kaiwekite.
  Dike rock.                         Kedabekite.
  Diorite.                           Kentallenite.
  Ditroite.                          Kenyite.

_Igneous material._--Continued.

  Keratophyre.                       Perlite.
  Kersantite.                        Phanerite.
  Kimberlite.                        Phonolite.
  Kobalaite.                         Pierite.
  Krablite.                          Pitchstone.
  Krageröite.                        Plagiaplite.
  Kulaite.                           Plagioclastic.
  Kyschytymite.                      Plumasite.
  Lamprophyre.                       Plutonic rock.
  Latite.                            Pollenite.
  Laugenite.                         Porphyry.
  Laurdalite.                        Pulaskite.
  Laurvikite.                        Pumice.
  Lava.                              Pyroxenite.
  Lestiwarite.                       Rhombenporphyry.
  Leucite basalt.                    Rhyolite.
  Leucite tephrite.                  Rizzonite.
  Leucitite.                         Rockalite.
  Leucocratic.                       Santorinite.
  Lherzolite.                        Sanukite.
  Limbergite.                        Saxonite.
  Lindoite.                          Scyelite.
  Liparite.                          Shastaite.
  Litchfieldite.                     Shonkinite.
  Lithoidite.                        Shoshonite.
  Luciitss.                          Soda granite.
  Lujaurite.                         Sölvsbergite.
  Madrupite.                         Sommaite.
  Maenaite.                          Spessartite.
  Magma basalt.                      Sussexite.
  Malchite.                          Syenite.
  Malignite.                         Taimyrite.
  Mangerite.                         Tawite.
  Mariupolite.                       Tephrite.
  Melaphyre.                         Teschenite.
  Melilite basalt.                   Theralite.
  Mesanite.                          Tilaite.
  Mica peridotite.                   Tinguaite.
  Minette.                           Tjosite.
  Missourite.                        Tonalite.
  Monchiquite.                       Tonsbergite.
  Mondholdeite.                      Tordrillite.
  Monmouthite.                       Toscanite (?).
  Monzonite.                         Trachy-andesite.
  Mugearite.                         Trachyte.
  Naujaite.                          Trap.
  Nelsonite.                         Troctolite.
  Nephelinite.                       Umptekite.
  Nevadite.                          Unakite.
  Nordmarkite.                       Ungaite.
  Norite.                            Urtite.
  Obsidian.                          Valbellite.
  Odinite.                           Venanzite.
  Orbite.                            Verite.
  Orendite.                          Vitrophyre.
  Ornöite.                           Vogesite.
  Orthophyre.                        Volcanic rock.
  Ortlerite.                         Volhynite.
  Ouachitite.                        Vulsinite.
  Paisanite.                         Websterite.
  Pantellerite.                      Wehrlite.
  Pegmatite.                         Windsorite.
  Peridotite.                        Wyomingite.
  Perknite.                          Yamaskite.




INDEX.



  A.

  Abbreviations, forms of.  55-67
  Adhesive materials, choice.  37
  Alaska, maps of, reuse of.  17
  Albertype. _See_ Photogelatin processes.
  Apparatus, photographs of, preferred to sketches.  29
  Approval of finished drawings, features to be covered by.  38
    of illustrations, regulations governing.  80
  Areas, patterns used to distinguish.  23
    patterns used to distinguish, plate showing.  62
  Army, Corps of Engineers of the, maps published by.  15
  Artotype. _See_ Photogelatin processes.
  Atlases, published, use of.  15


  B.

  Base maps. _See_ Maps, base.
  Bleaching photographic prints, method and solutions for.  69
  Border for maps, width and use of.  57-58
  Bristol board, kind Mid sizes used.  24,66
  Brash and pencil drawings, materials and methods used
    in making.  66-67, 69
  Brushes, kinds and sizes used.  66-67,71


  C.

  Celluloid transferring, process of.  47
    requisitions for.  47
  Cerotype process, description and advantages of.  80-81
  Changes in engravings, possible kinds of.  38-39, 90
  Changes in original material, draftsman to consult author on.  65
  Chemical elements, names and symbols of.  98
  Chromolithography, description of.  87-80
  Civil divisions, lettering of.  53, 54
  Coal beds, indication of thickness of.  31
  Coast and Geodetic Survey charts, use of.  15
  Collotype. _See_ Photogelatin processes.
  Coloring materials, use of.  26
  Colors, standard, for geologic maps.  62-63
    use of, for ground-water features.  21-23
      on original geologic maps.  27-28
  Commas, form of.  54
    use of, in numbers.  54
  Contours, drawing of.  48-50
  Cooperation, mention of.  13
  Copper, engraving on.  89, 90
    etching in relief on, process and advantages of.  75
  Copying methods of.  46-48
  Corrections. _See_ Changes.
  Cost of photo-engravings.  75, 78, 80, 81
  County maps, use of.  15
  Crayons, wax, use of.  26, 50, 51
  Credit for data of maps, indication of.  13
  Crystals, drawings of, making and lettering of.  70
  Cultural features, lettering of.  53-54
    list of.  52-53
  Curves, date showing.  64
  Cuts. _See_ Engravings.


  D.

  Details of a geologic map, plate showing.  58
  Diagrams, drawing and lettering of.  64
    features of, plate showing.  64
    original, general requirements for.  28-20
  Director of the Survey, order by.  9
  Divisions of plates and figures, serial letters and numbers for.  12
  Drafting table, shadowless, description of.  47-48
    shadowless, use of.  29, 48, 50
  Draftsmen, detail of, to aid author.  9
    detail of, to prepare base maps.  13-14
    experience and reading required by.  41-42
    general treatment of material by.  42-43
  Drainage features, depiction of.  51-52
  Drawing instruments, list of.  42
  Drawing materials, kinds used.  23-26, 66-67, 69, 71
  Drawings, authors', draftsmen may aid in making.  9
    authors', editorial revision of.  38
    finished, general requirements for.  41-42
    requests for photographs of.  34
  Duplicates of engravings, charges for.  38


  E.

  Effectiveness of illustrations, elements that produce.  7, 30
  Electrotypes of engravings, charges for.  38
  Elements, chemical, names and symbols of.  93
  Engraving on stone, process of.  89-90
    _See also_ Lithography.
  Engravings, changes in.  38-39
    original, time of keeping.  37
  Erasers, injury to paper by.  67
    kinds used.  25, 67-68
  Erasures, smoothing paper after.  68
  Explanations on maps, arrangement and lettering of.  19, 58-50


  F.

  Figures, differences from plates.  10-11
    divisions of, serial letters for.  12
    methods of inserting, plate showing.  12
  Formations, geologic, use of letter symbols for.  20-21
  Fossils. _See_ Specimens.
  Four-color process, advantage of.  80


  G.

  Gas wells, symbols for.  21
  Generalization, true, meaning of.  17
  Geographic tables and formulas (Bull. 650), use of.  44, 45
  Geologic periods of time, names of.  92
  Gouache, use of.  67, 69
  Great Lakes surveys, maps published by.  15
  Greek letters, forms, names, and English sounds of.  93
  Ground-water features, symbols representing.  21-23


  H.

  Hachuring, use of.  50
  Half-tone engraving, preparation of copy for.  77-78
    process and advantages of.  75-78
    three-color process of.  78-80
  Half tones, changes in.  39
    prints of, showing effects produced by different screens.  56
    requirements for printing.  11
  Heliotype. _See_ Photogelatin processes.
  Hill shading, use of.  60-51
  Hydrographic features, lettering of.  54
    representation of.  51-52
  Hypsographic features, lettering of.  54


  I.

  Illustrations, kinds of.  10-11
  Inks, kinds used.  25, 67
    methods of using.  25
  Inserting plates and figures, methods of, plate showing.  12
  Instruments, draftsmen's, list of.  42


  J.

  Japanese transparent water colors, use of.  26


  L.

  Land Office maps, scales and detail of.  14-15
  Latitude, length of 1° of, at intervals of 10°.  91
  Lending of photographs and drawings, rules governing.  34
  Letter symbols, use of, on geologic maps.  20-21
  Lettering, directions for.  53-55
    for lithographing.  90
    for names of streams.  52, 54
    on diagrams.  64
    on drawings of crystals.  70
    on original maps.  19
    on plans and cross sections of mines.  65-66
    reduction sheet used in, plate showing.  54
    use of type for.  54-55
  Light, direction and gradation of.  66
  Lithographs, printing and insertion of.  11
  Lithography, original process of.  83-85
    _See also_ Engraving on stone.
  Longitude, length of 1° of, at latitudes 0° to 90°.  91


  M.

  Map of the world, millionth-scale, use of, for base maps.  14
  Maps, areal patterns for, drawing of.  61-62
    bar scales for.  59-60
    base, conventional symbols used on. 45-46
      including new data, how obtained.  13-14
      indication of sources on.  13
      of the United States on small scales, use of.  15
      published maps available for.  14-17
      reuse of, to be approved.  13
    black and whits, patterns used on, plate showing.  62
    borders for.  57-68
    cultural features on.  52-53
    enlargement and reduction of.  18
    explanations for.  19, 58-59
    geologic, details of, plate showing.  58
      printing of.  87-89
      standard colors for.  62-63
    hydrographic features on.  61-52
    lettering on.  53-65
    materials used for drawing.  23-28
    orientation of.  18
    original, margin required on.  19
    original base, amount of detail on.  17
      must be free from colors and symbols.  28
      preparation of.  13-14, 17-18
    original geologic, method of coloring.  27-28
    projection for.  18-19, 43-45
    reduction or enlargement of, marking for.  63-64
    relief on.  48-51
    standard scales for.  18
    symbols used on.  20-23
      drawing of.  61
      plates showing.  20, 46
    titles for.  58
    topographic, scales of.  14-15
  Mathematical signs, forms and names of.  94
  Measures, linear, metric equivalents of.  92
  Measuring scales for map projection, use of.  44
  Meridians used on public-land maps, diagram showing.  16
  Metric measures, English equivalents of.  92
  Millionth-scale map, use of.  14
  Mine plans, conventional lines for.  29
    features of.  65-66
    symbols used on, plate showing.  20
  Minerals. _See_ Rocks.
  Mississippi River Commission, maps published by 15


  N.

  Names of rocks.  94-97
  National forest maps and proclamations, use of.  15


  O.

  Offset process, description of.  87
  Oilwells, symbols for.  21
  Opaquing, meaning of.  18, 47, 86
  Orientation of maps, requirements for.  18
  Original drawings, general treatment of, by draftsmen.  42-43
    preparation of.  12-40
  Outdoor sketches, redrawing of.  69-70


  P.

  Panoramas, construction of.  71
  Paper, kinds used for drawings.  23-24, 60, 61, 66, 69
  Pastes, use of.  37
  Patterns, areal, method of drawing.  61-62
    areal, plate showing.  62
  Pen drawings, materials and methods used in making.  67-68, 68-69
  Pencils, colored, use of.  26
    drawing, quality and grades of.  25, 66
  Pens, kinds of, used for drawing.  25, 48, 67
  Photoengraving, cost of.  75, 78, 80, 81
    general features of.  72-73
  Photoengravings, printing and insertion of.  11
  Photogelatin processes, description of.  82-83
  Photographs, adaptation of.  83
    bleaching of.  69
    care needed in taking and handling.  32, 33, 39-40
    copyrighted, consent for use of.  33-34
    duplicate prints of, requests for.  34
    mounting and numbering of.  33, 36-37
    poor, mating of drawings over.  68-69
    preparation of, for half-tone engraving.  77-78
    record of source of.  34
    selection of.  32-33
    retouching of.  68, 70-71
    suitability of. 9
    unpublished, issue and use of.  34
  Photolithographs, changes in.  39
  Photolithography, description of.  86-87
  Planographic process, description of.  87
  Plans of mines, drawing and lettering of.  29, 65-66
    symbols used on, plate showing.  20
  Plates, differences from figures.  10-11
    divisions of, serial letters and numbers for.  12
    grouping small illustrations on.  36-37
    methods of inserting, plate showing.  12
  Political divisions, lettering of.  53, 54
  Post-route maps, scales and detail of.  15
  Projection for maps, preparation and checking of. 18-19, 43-45
  Proofs, changes in.  76
    correction of.  38-39
    duplicate, supplying of.  30
    submittal of.  38
  Public-land maps, meridians, parallels, and township lines used on,
    diagram showing.  16
  Public works, lettering of.  53
  Punctuation marks, forms of.  54
  Purpose of illustrations in Survey reports.  8, 40


  R.

  Railroad surveys, data for maps obtainable from.  15
  Railroads, names of, on maps.  57
  Reduction of maps, marking drawings for.  63-64
    means of.  18
  Reduction sheet for lettering, plate showing.  54
    use of.  55
  Relief, methods of expressing.  48-51
  Reproduction of illustrations, processes for.  72-90
    relation of, to the drawing supplied.  7, 40
  Reticulation, sketching by.  47
  Retouching of photographs, materials and method used in.  68, 70-71
  Reuse of illustrations, procedure for.  37-38
  Rocks, igneous, names of.  95-97
    metamorphic, names of.  95
    sedimentary, names of.  94-95
    symbols used to distinguish.  32
    _See also_ Specimens.
  Roman numerals, numbers expressed by.  93
  Rubber, liquid, use of.  37


  S.

  Scales, bar, forms of.  50-60
    measuring for projection of maps.  44
    standard, of maps.  18
  Scope of this manual.  7
  Screens, half-tone prints showing effects produced by.  56
  Selection of illustrations, considerations governing.  8-9
  Sections, columnar, original drawings for.  31
    columnar, symbols used in, plate showing.  32
    structure, combination of, with views of topography.  30-31
      drawing of.  64-65
      original drawings for.  29-31
      symbols used in, plate showing.  32
      vertical exaggeration of.  30
  Shading, kinds used.  67
  Signs, mathematical, forms and names of.  04
  Sises of illustrations.  11-12, 40
  Specimens, borrowed and fragile, care of.  35
    drawings of, methods of making.  60-68
    paleontologic, transmittal of.  35
    photographs of, how printed.  68
    how used.  34-85
  Springs, symbols for.  22, 23
  State maps, use of.  15
  Stipple, production of.  50, 51
  Stone, engraving on.  89-90
  Streams, drawing of.  51-52
    lettering names of.  52
  Submittal of illustrations.  10
  Symbols, drawing of.  20, 61
    for ground-water features, uniformity needed in.  21-23
    for maps and mine plans, plates showing.  20, 46
    uniform use of.  20, 45-46
    for oil and gas wells, features of.  21
    for structure and columnar sections, plate showing.  32
    lithologic, use of.  32


  T.

  Three-color half-tones, process of making.  78-80
  Titles of illustrations, arrangement and place of.  58
    printing of.  19-20
    wording and lettering of.  19
  Tooling on half-tones, effects obtained by.  77, 78
  Topographic atlas sheets, scales of.  14
  Tracing, method of.  46-47
    use of colors in.  46-47
  Tracing linen, use of.  24-25
  Transferring, celluloid, process of.  47
    celluloid, requisitions for.  47
  Type, lettering with.  54-55
    styles and sizes of.  55


  V.

  Value of illustrations in Survey reports.  8
  Vara, length of.  92
  Vignetting, effect obtained by.  78


  W.

  Wall map of the United States, use of, for basemaps.  14
  Water colors, use of.  26, 67, 71
  Waterlining, use of.  52
  Wax engraving, process and advantages of.  80-81
  Wells, symbols for.  22, 23
  Wood engraving, process of.  81-82


  Z.

  Zinc etchings, changes in.  38-39
    drawings for.  74
    insertion of.  11
    making and advantages of.  73-75


[Illustration: circle]


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Transcriber's Note

Paragraphs split by illustrations were rejoined. Where Greek
characters occurred in the original, [Greek: ] was substituted for
them. To see these characters, view the UTF-8 or HTML version.