Produced by Chris Curnow, Paul Marshall and the Online
Distributed Proofreading Team at http://www.pgdp.net (This
file was produced from images generously made available
by The Internet Archive)






Transcriber’s Notes:

  Underscores “_” before and after a word or phrase indicate _italics_
    in the original text.
  Equal signs “=” before and after a word or phrase indicate =bold=
    in the original text.
  Small capitals have been converted to SOLID capitals.
  Illustrations have been moved so they do not break up paragraphs.
  Typographical errors have been silently corrected.
  The three advertisements at the beginning of the book have been
    moved in front of the thirteen advertisements at the back of the
    book.




                            CENTRAL-STATION
                           ELECTRIC LIGHTING
                                 WITH
                   NOTES ON THE METHODS USED FOR THE
                     DISTRIBUTION OF ELECTRICITY.

                                  BY
                         KILLINGWORTH HEDGES,

       MEMBER OF THE INSTITUTION OF CIVIL ENGINEERS, AND OF THE
           SOCIETY OF TELEGRAPH ENGINEERS AND ELECTRICIANS.

                            [Illustration]

                                LONDON:
                     E. & F. N. SPON, 125, STRAND.
                    NEW YORK: 12, CORTLANDT STREET.

                       [_All rights reserved._]




PREFACE.


The art of lighting by Electricity practically dates from ten years
ago, and it has during that period received the constant attention of
both Electrical Engineers and others, who have applied the greatest
scientific knowledge. The result of all this energy appears to be
discouraging. Five hundred thousand pounds have been subscribed to
carry on the business, and it is doubtful whether the companies which
survive have a market value of one-tenth of that sum. The experience
may have been bought too dearly, but the era of Central-Station
Electric Lighting, which has now commenced, ought to re-establish the
position of Electricity in financial circles, and afford a safe and
profitable outlet for the surplus capital of the investor who buys gas
and water shares to pay four per cent.

The distribution of electricity from a central-station, which was the
subject of Sir William Siemen’s Presidential Address at the Society of
Arts in 1882, is not only accomplished from the scientific point of
view, but is also a commercial success: the power of flowing water, or
the potential energy stored up in coal, wood, or other fuel, can be
utilised for lighting our streets and houses at night, and during the
day may be transmitted by means of electricity in the easiest possible
way, and supplant the gas-engine for driving small machinery.

A paper entitled “Central-Station Electric Lighting” was contributed by
the Author to the Institution of Civil Engineers, and was published in
Part II. of the Minutes, 1886-87; the subject-matter has been extended
and brought up to date, with the object of giving a description of the
systems which are practically employed in Central-Station Lighting at
home and on the Continent. Details respecting the generating plant at
these stations are omitted on purpose; technical terms would also be
avoided if possible; failing this, it is hoped that the accompanying
Glossary will explain what is unfamiliar.

The amendment of the Electric Lighting Act of 1882 has given a fresh
stimulus to the industry, and many new enterprises for distributing
electricity from Central-Stations are being prepared, and it is to
be hoped that the public will profit by former experience, and will
discriminate between the good and the bad schemes which will be offered
to them.

The organizing facilities possessed by Gas Companies make it desirable
that they should follow the example of the American Companies, and
take up the business of supplying electricity. The existing powers of
private companies might have to be altered, but those municipal
authorities who own the gasworks could certainly distribute electricity
from a central-station, which might be installed at the present works.
Local authorities have certain advantages over private companies
owing to the purchasing clause of the Electric Lighting Act, also the
power to borrow money under this and the Local Loans Act of 1875;
should there be no department to carry out the business of supplying
electricity, the generating plant could be maintained and worked by a
contractor for a fixed annual sum.

The remarks of Lord Herschell that the “electric light is more used in
the South Sea Islands than in this country” ought to be taken as not
so much referring to want of enterprise on the part of capitalists and
engineers, but to the Electrical Facilities Act of 1882, which has been
appropriately termed a very “boa-constrictor.”

                                              KILLINGWORTH HEDGES.
    25, QUEEN ANNE’S GATE,
        WESTMINSTER, S.W.
            _September, 1888._




INDEX OF TERMS.


    AMPÈRE-HOUR.—A current of one ampère strength
        for one hour.
    CURRENT, CONTINUOUS.—The flow of electricity
        in one direction.
    CURRENT, ALTERNATING.—The intermittent flow
        in two directions.
    CONDUCTOR.—The wire through which the current
        passes.
    CIRCUIT, PRIMARY.—With transformers, the
        conductor or leads attached to the dynamo.
    CIRCUIT, SECONDARY.—With transformers, the
        conductor from the transformer to the lamps.
    C. P.—Abbreviation of Candle-power.
    E. M. F.—Abbreviation of Electro-motive force.
    LIFE OF INCANDESCENT LAMPS.—The duration of
        the filament which produces the light.
    POTENTIAL.—Difference of E. M. F., or High
        and Low-Tension.

       _See also Glossary, or Explanation of Terms_, page 107.




AN ELECTRICAL CENTRAL-STATION.


As the term “central-station” associates itself with some pretentious
building, such as a railway terminus, it may be advisable to remark
that the similarity is only in the words, and that central-station is
an abbreviation of central generating station, or building designed to
contain the plant for the public supply of electricity. In the early
days of electric lighting the transmission of electricity to a distance
was considered an impossibility; we find the late Sir William Siemens,
in his Presidential Address at the Society of Arts on the occasion of
the opening of the session in 1882, stating “that a quarter of a mile
in every direction from the lighting station was the area which would
be as much as could be economically worked;” and, in order to tap the
most paying district, it was proposed to establish a station in the
most central spot. Sir William Siemens suggested the utilisation of
the public squares, which could be excavated to a depth of twenty-five
feet, and then arched over to the existing ground level, and in this
covered space the engines, boilers, and dynamos were to be fixed;
the only erection above the surface was the chimney, which was to be
of ornamental design and combined with the ventilating arrangements
of the subterranean chamber. The great inventor, who so ably filled
the presidential chair at the meeting where these words were spoken,
would be astonished to find that in London one electric lighting
company has already erected seventy miles of overhead wire, and that
customers are supplied miles away from the so-called central-station.
The changed position of electricity is due to the introduction of the
transformer by Goulard, who showed, at the Turin Exhibition of 1884,
that a high-tension current could be transformed into a low-tension
working current of safe potential, fifty miles away from the generator,
in a successful and economical manner, and that the generating station
might, therefore, be located outside the area to be lighted. In large
cities this is a great advantage, the value of land often precluding
the erection of a big station in the working area; for this reason
small stations are often arranged in basements, under a large building,
which are, as a rule, specially designed. This plan is somewhat similar
to that adopted in the United States, where it is not unusual to
find a successful installation in a basement and sub-basement, the
general arrangement being of similar character to the engine-room of a
steamship.

A station is being erected in Philadelphia on a ground space of 72
feet × 100 feet, which is to supply 60,000 lights; the building is
six-storied, the dynamos are on the first floor, the boilers on third,
the coal stores on fourth, and the offices on the fifth.

The term “block station” is also used in the United States and in
Germany, and is applied to an installation which lights a group of
buildings or block without crossing any streets, and consequently
without having any wayleave or permission from local authorities.


CENTRAL-STATION CONSTRUCTION.

An American electrical engineer graphically sums up this question
in the following manner:—“There are two ways of starting a
central-station for electric lighting—the investment or the
speculative plan, or the fair means or the foul. The first has
its legitimate end, but the latter is the border ruffian or
money-or-your-life policy, which enters a territory already
sufficiently covered, not for fair competition, but to make money by
being bought out.” Happily, here, we have at present only to deal
with the first plan, and the question naturally arises, “Is electric
lighting a paying investment?” It certainly will not be if the object in
view is only to compete with gas in a limited district where perhaps
it is being sold at 2_s._ 6_d._ per 1000 feet, for, as long as there
is a ready market for the coke and other by-products, gas will remain
in possession of the field. The heat from gas, which is found so
undesirable by the wealthier classes, is advantageous to those who
perhaps cannot afford a fire; in fact, gas has been truly called
the “poor man’s friend,” and, until electricity can be supplied at
a nominal price, it will be useless to expect any revenue from the
poorer districts of large cities. Quite an opposite result may be
looked for when the electric mains are laid at the doors of the wealthy
householder, or through the business neighbourhoods. Shop-owners
especially are found to immediately take up electric light, from the
fact that no fumes are given off to destroy goods or tarnish silver
or gilding, and because it can be so easily applied in a shop window
so as to efficiently light the contents without producing shadows.
The great object to be aimed at in selecting a district to be served
from a central-station is a “constant demand,” and for this reason
it is advantageous to include a business neighbourhood with shops,
public-houses, and restaurants, which require the light for a definite
period every day, and probably will each take more than double the
amount of an ordinary dwelling-house; in fashionable neighbourhoods
especially, it is not unusual to find a large number of houses vacated
at the close of the season, the interest on that portion of the
electric system which is unemployed will have to be set against the
profits of other periods of the year.

The number of gas lights which are actually used at one time in a house
is found to average only two-thirds of the total number fixed, and
with electric light this number is reduced to one-half; economy is at
once the rule with electric light, partly because of the novelty of
the illuminant, and also on account of the facility of lighting and
extinguishing by simply turning a tap or switch. The number of hours
artificial light is wanted in a residential district may be taken at
about 1000 hours per annum, that is to say, the light is required for
about four hours a day in winter and two hours in summer; this amount
is very much exceeded in clubs, shops, and even in large houses, but
1000 hours is a safe figure, and, if the supply is taken by meter,
an annual payment equivalent to 1000 hours’ supply should be a fixed
amount to be paid for, whether used or not. Mr. Crompton estimates
that a Londoner, who is a tenant or owner of a house having three
reception rooms, ten bedrooms, and usual offices, spends about £25 a
year for his lighting, which is made up as follows:—gas bill, £15;
lamp, oil, candles, matches, about £10. There would be about fifty
burners fixed; and, supposing fifty electric lights to be substituted,
he could be supplied with electricity for £25 a year, at a fair profit
to the supply company if they charged 8_d._ per Board of Trade Unit,
as practice has shown that the total number of lamp-hours with fifty
electric lamps is not more than sixty-two, so that two Units,[1] or
1_s._ 4_d._ per day, would be sufficient for the lights he would
require.

[1] Unit; see page 7.

The diagram, Fig. 1, taken from a London residential district, shows
how the number of lamps on at one time vary; the district is supposed
to be wired for 10,000 lamps, and the plant as equal to the supply of
600 kilowatts, or 600,000 watts; the number of lamps is small until
about 3 o’clock, when it gets dusk on a winter afternoon; it then
increases steadily until about 6.30 o’clock, when the curve goes up
with a rush; about this time a great number of people are preparing for
dinner, and probably the lights are on both in the dining-room and
bedrooms. The curve falls, and at about 8 it begins to sink gradually
until 10 o’clock; a great many people appear to go to bed about this
time, but a few sit up to 1 o’clock; until 6 the next morning hardly
any supply is taken, when the servants get up and prepare the rooms
for the day. The diagram, Fig. 2, is taken from the Edison Company’s
central-station at Cincinnati, and agrees fairly with the London
demand for light. Another interesting fact has been ascertained from
the observations taken at the Mauer Strasse station in Berlin, namely,
that the output varies with the temperature, it goes up or down with
the thermometer. The reason is easily explained; gas is laid on side
by side with the incandescent lamps, and the burners are first lighted
when it is cold to warm the apartments; in warm weather the electric
light alone is used. From these and other diagrams the very important
fact has been obtained, that the average daily output of a station
throughout the year is less than one-third of the total capacity of
the generating machinery, so that, although the station from which
the diagram in Fig. 1 was taken could maintain 10,000 16 candle-power
lamps simultaneously alight, the average daily output of electricity
would only equal 3500 constantly lighted; and, as the first cost of the
station is dependent on the size of the plant, the saleable output is
the important factor which governs the profits.

[Illustration: FIG. 1.]

[Illustration: FIG. 2.]


CHARGES FOR ELECTRICITY.

The well-known expression “per 1000 Cubic Feet” is not applicable to
electric light, and, instead, the Board of Trade Unit is employed.
By this term Unit is meant the quantity of energy contained in a
current of 1000 Ampères flowing under an Electro-motive Force of One
Volt during One Hour. In the early days of electric lighting the term
Volt-ampère was used, and has for convenience sake been shortened to
Watt; that is, the Volt or Unit of Electro-motive Force (or pressure)
is multiplied by the Ampère or Unit of current.

The Board of Trade Unit is, therefore, a Thousand Volt-ampères or Watts
per hour.

For example: 16 candle-power Swan lamps are assumed to take 60
Watts, which, if the electrical pressure is 100 Volts, would mean a
consumption of 0·6 Ampère; and, as an Electrical Horse-power equals 746
Watts, 12·4 lamps should theoretically be obtained per Horse-power,
which is, however, reduced in actual practice to 10 at the most, often
less.

The charge per Unit supplied by meter varies in England from 1_s._ to
7_d._

    Price for electric            Equivalent price for gas of equal
          light.                               light.

    _s._  _d._                _s._   _d._
     1     0     } per Board { 6     10      per 1000 cubic feet.
     0     9     }     of    { 5      1½      ”         ”
     0     7¼    }   Trade   { 4      2       ”         ”
     0     6     }   Unit.   { 3      5       ”         ”


_Comparison of Cost of Gas and Electricity._

These prices, of course, include the manufacturer’s profit as well as
the loss in transmission through the mains and expenses of connecting
up to the consumer. The actual manufacturing cost of a station
maintaining 10,000 lights should not be more than 3_d._ per Unit, or
equivalent to gas at 1_s._ 8½_d._ per 1000 cubic feet.[2]

[2] See Table IV., page 87.

As petroleum lamps are used for the street lighting of many foreign
and colonial towns, the question arises, “Will it pay to substitute the
electric light?” Comparing the light given by a kerosene or petroleum
lamp with that from the incandescent electric lamp, the cost is greatly
in favour of oil; and, in fact, where the price of kerosene is under
1_s._ per gallon, electricity cannot compete if labour is cheap. On the
other hand, the trimming, lighting, and keeping in order of a number of
lamps scattered over a large area greatly augments the working cost, to
which must be added the breakages of chimneys, expense of wicks, also
the danger of fire. It is the safety of electricity which has caused
it to supplant oil both for public and private lighting in American
cities; even where the price of kerosene is not more than 6_d._ per
gallon there is a demand for the electric light, which is by far the
dearer illuminant, after making a liberal allowance for labour in
cleaning, filling, and lighting the oil lamp, also for depreciation of
the burners.


_Arc and Incandescent or Glow Lighting._

[Illustration: FIG. 3.]

Electric lighting can be obtained by means of arc or incandescent
lamps. The arc light is now well understood to be caused by the
extremely high temperature of the end of one or both the carbon
electrodes. The voltaic arc, Fig. 3, is formed by the minute particles
of carbon in a high state of combustion which the current appears
to break off and carry from one electrode to the other, the light,
however, being mainly due to the incandescence of the crater shown in
Fig. 3 on the upper carbon. In the incandescent or glow lamp light
is produced by the passage of a current of electricity through a
continuous fine thread or filament of carbon which becomes white-hot,
the destruction of the filament being prevented through its enclosure
in a glass bulb from which the air is exhausted. Figs. 4 and 5.

The first method is suitable for the lighting of streets where a
high-class illumination is required; also will be wanted for the
external lighting of shops, public-houses, and places of amusement, so
that arrangements must be made for arc lighting. The usual plan is to
charge at the same rate per Unit by meter as the incandescent lamps,
but to make an additional charge of 5_s._ to 7_s._ 6_d._ per lamp per
quarter for rent, and a further charge of 3_s._ per week for cleaning
and trimming.

The principal types are the Edison and the Swan, Fig. 4 and Fig. 5.

Incandescent lamps can be obtained to order from 1½ candle-power
upwards, but the 16 candle-power (nominal 20) or the 8 candle-power
(nominal 10) lamps are almost invariably employed. The latter give the
best effect, and can be worked to 10 candle-power without much risk,
they take about 30 watts as against 60 watts for the 16 candles; and
are not uneconomical, for nearly double the number can be worked with
the same energy. A new type of glow lamp, called the “Sunbeam,” has
been recently introduced, which contains a thick filament, and gives a
light of from 200 to 1500 candle-power, and can be employed instead of
an arc lamp with the same economy as the ordinary 16 candle-power type.

[Illustration: FIG. 4. FIG. 5.]


_Life of Incandescent Lamps._

In estimating the annual cost of lighting, the renewals of lamps must
be taken into account; and although some lamps have worked 3000 or even
4000 hours, a life of 1000 working hours is the highest average it is
safe to assume in practical work under even the best conditions, that
is, using secondary batteries and never over running. The average
life of 130 lamps on H.M.S. troopship _Malabar_ was 3799 hours each,
the shortest life being 638½ hours for 18 yard-arm lamps of 32
candle-power. If the current is allowed to fluctuate, the average life
would be very much less; it is an unsettled question whether long-lived
lamps are really economical, by reason of the blackening of the globes,
which takes place after the lamp has been worked some time, and is
probably due to small particles of carbon thrown off from the filament
being deposited on the glass. It has been suggested that attrition of
the filament is going on all the time the lamp is at work, and that
the heated atoms striking against the filament may account for the
blackening, in that the mean free path of the atoms would be greater
in a perfect vacuum than in the air, consequently they would abrade
the filament with considerable force. If lamps were sold at 1_s._ each
instead of 3_s._ 6_d._, which is now the price for not less than a
thousand, it would be more economical to change them at the first signs
of blackening, even if the life did not exceed 500 hours.

The diagram, Fig. 6, has been so arranged that the amount of light
required in a given district can be ascertained for any period of the
day or night; it has been calculated from the observations taken daily
at one of the Berlin central-stations by the engineer to the company.

Six hundred and forty watts are assumed, for the purposes of the
diagram, to be the equivalent of a horse-power, instead of 736, as the
German electrical horse-power is 736 watts instead of 746 watts.

[Illustration: FIG. 6.]

The table, Fig. 6, has two vertical scales, A and B, each giving the
kilowatts[3] and corresponding horse-power. A is drawn to a scale ten
times greater than B, with the object of noting the smaller amount of
lights required for street illumination. The horizontal line is divided
into hours, and represents a day’s lighting in the middle of December
and the end of July, so as to show the maximum and minimum amount of
current that will be required. In the lighting of a town there are
two classes of illumination, the amount taken by the public, which is
uncertain, and that employed for street lighting, which is a known
quantity.

[3] 1000 watts.

The curves, II and II A, represent the private lighting of houses,
hotels, theatres, and shops of different kinds in December and in
July, the curve, II A, being in dotted lines clearly shows what a vast
difference there is in the amount of light, and consequently the amount
of energy required in the generating station, as compared with curve
II, which is taken when the days are longest.

The rectangles, I and I A, show the street illumination, and are drawn
to suit scale A; half an hour after sunset all the lamps are turned on,
and the work reaches its maximum suddenly, and continues the same until
12 o’clock, when, according to the municipal decrees, it either falls
one or two gradations until half an hour before sunrise, when all the
lamps are extinguished. The calculations are based on the assumption of
640 watts to the horse-power, instead of 736, which is the theoretical
efficiency of a German horse-power.

If a number of diagrams are taken on this method for different periods
of the year, the constant work can be ascertained. This knowledge is
most valuable when calculating the most economical area for the mains,
which is then easily accomplished by means of Forbes’ tables, which are
based on Sir William Thomson’s well-known rule.

The lines, 2 and 2 A show the constant work at the same two
periods of the year from which the diagrams are taken. The constant
work at the end of December will be found to amount to 20 per cent.
of the total work, and that at the middle of June to 15 per cent. By
summing up the average work for all the days in the year we obtain the
cost per annum, and adding to this the expense of management, interest,
&c., and knowing the local conditions, we can fix what proportion of
the day’s work is admissible as loss. With the Edison system at Berlin,
5 per cent. is taken as average loss; thus, at the end of December,
it amounts, with the maximum number of lights, to 18·8 per cent., and
with the minimum to 1·1 per cent.; in the middle of July the maximum
is 15·8 per cent., and the minimum 0·5 per cent. The dynamos must, of
course, be of sufficient power to be able to overcome this loss, which
only shows itself periodically; therefore the generating plant may
be constructed to give, nominally, 20 to 30 per cent. less than the
maximum work, and be capable of being pushed to the full amount for a
short time only.


THE POSITION OF CENTRAL-STATION LIGHTING.

Uncontrolled financial speculation, aided by the stringent clauses of
the Electric Lighting Act of 1882, have been a great deterrent to the
extension of old or the introduction of new schemes for the supply of
electricity to the public in the same manner as gas. The President of
the Board of Trade, replying to a question in the House of Commons,
said that, “since the passing of the Electric Lighting Act of 1882,
fifty-nine provisional orders and five licences had been granted to
companies, and fifteen provisional orders and two licences to local
authorities. He was not aware that, in any single case where these
powers had been obtained, they had been exercised.” Up to the present
time no company supplying electricity has been under the necessity of
applying for compulsory powers, and has either obtained permission
from the local authorities to take up the streets, or has carried the
electric mains over the houses, and, regardless of the question of
overhead wires, has depended on wayleaves granted by the too-confiding
householder, who has no idea that his roof is supporting a cable
weighing 1¾ tons to the mile.

An amendment of the Act of 1882 has passed both Houses without
hindrance, and has received the Royal assent. It provides that in the
case of Provisional Orders the period after which the undertaking may
be bought up by the Local Authority shall be extended from twenty-one
to forty-two years, and that portion of the previous Act which referred
to the compulsory purchase of the undertaking by a local authority at
the end of the term has been altered, and more favourable terms given
to the electric companies.

On the Continent, and in the United States, where each city may be said
to legislate for itself in matters relating to the general welfare of
its citizens, the electric lighting industry is in a very different
position, and central-stations are either established or about to
be started in every important town. There were, in 1887, 121 Edison
central-stations alone, supplying over 323,000 incandescent lamps, and
paying dividends from 6 to 14 per cent. The Westinghouse Company, who
use a transformer system which is a modification of the Goulard and
Gibbs, have a hundred stations, maintaining 191,000 lamps, although
the first Westinghouse plant was put down only three years ago. The
progress in the United States is so rapid, and there are so many
successful applications of central-station lighting, that the subject
becomes too large to be even summarised, so that it is proposed to
treat in the following pages with some of the principal installations
on the Continent and at home.

Travellers abroad are accustomed to find electric lighting installed in
the most out-of-the-way places, especially in Switzerland, where water
power is abundant and is utilised to generate electricity, so that in
small hamlets arc lighting is often employed, and the visitors to the
local hotel will find it lit throughout by electricity. Electric light
stations in England are, with one exception, small in comparison with
those on the Continent. The most important is that at the Grosvenor
Gallery, London, which has increased from small beginnings until
it now supplies 20,000 glow lamps on sixteen circuits, the total
length of which is seventy miles. The next largest, which have been
in practical work for some time, are the Brighton and Eastbourne
stations, from which small installations of glow and arc lights are
maintained in various districts of the two towns. That the question
of cost or trouble, and the annoyance of machinery when erected in a
dwelling-house, do not altogether prevent the adoption of a superior
light, is clearly proved by the increasing number of householders, who,
after waiting in vain for electricity to be brought to their doors,
have set up the plant necessary to produce it themselves, and find no
practical difficulty in doing so. There are also many important public
works where electric light has been exclusively adopted. For instance,
at the Tilbury Docks there are 1350 glow and 80 arc lamps, distributed
over an area of 300 acres, and including the lighting of an hotel, dock
sheds, warehouse, signal-boxes, and offices. The London, Chatham, and
Dover station at Victoria has also been electrically lighted for the
past three years, the current being obtained from a central-station,
which was erected for the purpose of supplying electricity to the
Victoria district, and for which a provisional order was obtained.
This, however, has since been abandoned, although £16,000 had been
expended on plant and buildings by the promoters, who preferred to
postpone the scheme rather than to submit to the onerous 27th clause of
the Electric Lighting Act. Another still larger installation has been
put down to supply electricity to the Paddington station and district
of the Great Western Railway, as far as Westbourne Park. It embraces
an area of sixty-seven acres, and is lighted by 4115 glow and 98 arc
lamps. The system adopted is that designed by Mr. J. E. Gordon, and has
now been successfully worked for some time; but the many accessories
which are introduced, such as telephones, telegraphs, and indicators,
make it complicated in comparison with gas, or even with the ordinary
electric light systems. The current is generated by two dynamos, each
weighing 45 tons, and having revolving magnet wheels 9 feet 8 inches
in diameter, 22 tons in weight, a third machine being kept in reserve.
These dynamos are separately excited, and produce alternating currents.
The electricity is led to a large switch-board for distribution
throughout the district by means of five sub-stations; and from this
board there branches a double system of mains, which run everywhere
side by side, one-half the mains being connected to the first machine
and one-half to the second, so forming an excellent arrangement for
the prevention of total extinction of the light. The mains running to
the sub-stations are on the divided system, which is introduced for
the purpose of saving copper, as in a solid cable the loss of pressure
is greatest when the full number of lamps is on, and decreases as the
lamps are extinguished. With the divided main system it is intended to
follow out Sir William Thomson’s formula, which equates the value of
the loss of head, and the interest on the saving on the copper. If for
a certain main this formula shows that a fall of 20 per cent. is the
most economical condition for working, then, since by the divided main
the pressure can be kept within a variation of 2 per cent. at the
distant end, it follows that a considerable saving can be effected over
an ordinary solid main. Special arrangements are adopted at Paddington
to keep the pressure constant, a fall of potential being allowed for;
thus at the engine-house the pressure is 150 volts, in the passenger
station it is 120 volts, and at Westbourne Park it is 100 volts. The
arc lamps are fed by the same mains, and are arranged two in series.

A small installation at Kensington Court, erected two years ago, for
the purpose of supplying the houses in the immediate neighbourhood,
has rapidly developed, and underground mains have been led in many
directions from the station, and a constant service of electricity
is provided for by means of secondary batteries. As this is the
first practical exposition of the secondary batteries’ system of
distribution, it is proposed to describe the installation under that
head. Central-stations are also at work in Liverpool, Leamington,
Taunton, Exeter, and there are also five large installations nearly
completed in London, besides the Kensington Court station, all of which
will probably be in full swing before the end of the year.

ELECTRIC LIGHTING from CENTRAL-STATIONS is now practically carried out
on five different methods.

      I. BY SECONDARY GENERATORS OR TRANSFORMERS, WITH ALTERNATING
          CURRENT.
     II. THE EDISON OR PARALLEL SYSTEM, WITH CONTINUOUS CURRENT.
    III. THE SERIES OR BERNSTEIN SYSTEM.
     IV. MULTIPLE SERIES.
      V. DISTRIBUTION WITH SECONDARY BATTERIES OR ACCUMULATORS.




CLASS I.

SUPPLY BY SECONDARY GENERATORS OR TRANSFORMERS.


The problem of electric lighting from central-stations is comparatively
easy if an area can be obtained immediately surrounding, and within a
short distance of, the station, with a right of way for laying down the
electric mains direct. This happy state of affairs has not yet been
attained, consequently the generating station has more often to be in
an out-of-the-way corner of the district to be lighted, and it would be
financially impossible to use low-tension currents with correspondingly
large mains. The difficulty has been overcome in several ways by the
use of high-tension currents in the mains, and has led to the adoption
of secondary generators or transformers of electricity, which by
induction supply a current of low potential in the house-service. The
first to make this plan a practical success was Mr. Goulard, to whom
the honour of the introduction is due, although his claims as the first
inventor have been recently upset by the decision of the Courts.

The relative economy of the supply of electricity by the use of a
transformer is clearly shown by the following diagram, Fig. 7. A, B,
and C give proportionately the area of cross section of the total mass
of copper necessary to supply 5000 16 candle-power glow lamps situated
at a mean distance of 4000 feet from the dynamo. A refers to the
Edison “three-wire” system, working at a potential or electrical
pressure of 200 volts with a fall of potential or loss of energy in the
distributing feeders of 10 per cent., average distance from dynamo 4000
feet—the usual conditions on which this system is worked. B shows the
size of conductor required for the same work in an installation based
on the transformer system, potential 1000 volts, allowing 2·5 per cent.
loss in the supply mains—only one-fourth as much as in the direct
Edison system at the same average distance from dynamo. If this loss
were increased to 10 per cent., and made equal to that in the direct
system, viz. 10 per cent., the size of the conductor would be that
shown at C.

[Illustration: FIG. 7.]

[Illustration: FIG. 8.]

The graphic diagram, Fig. 8, demonstrates what the relative cost would
be with each of the three conditions just named.

Mr. Goulard’s first practical application of the secondary generator
in this country was the lighting of the Underground Railway Stations,
in 1883, from Edgware Road to High Street, the generating dynamo being
fixed at the former place. These experiments, which were made by Mr.
Kenneth Mackenzie, attracted considerable attention at the time, but
it was not until the report of the jurors to the Turin International
Exhibition in 1885 was published that companies were formed to instal
the Goulard system for lighting an extensive district.

[Illustration: FIG. 9.]

The principle underlying all transformers is that of the induction
coil invented by Ruhmkorff in 1842, but described by Faraday in his
“Experimental Researches,” published in 1831-2.

Fig. 9 is a diagram of the ordinary induction coil; on a central core
is wound a short length of thick wire called the primary, and again
over this is wound a greater length of fine insulated copper wire which
forms the secondary coil. On sending a low-pressure current from the
generator round the thick wire, a much smaller high-tension current is
induced in the secondary. A contact breaker is employed to make and
break the current, or, as in the early instruments, a commutator may be
used to produce the alternations. When used as a transformer the action
is reversed, that is, a high-tension current is passed through the
primary coil, which is composed of a wire of small sectional area, the
high-pressure main connected to the dynamo also being small as compared
with the distributing cable leading from the transformer, which, acting
as a step-down induction coil, converts the electricity into a safe
working pressure.

[Illustration: FIG. 9A.]

Fig. 9 A shows the arrangement of the two separate and complete
circuits. D is the dynamo, P the primary coil, S the secondary, and L
the lamps arranged in parallel.

It is hardly necessary to go into the technical details of the various
improvements which have led up to the modern type of transformers; they
are summarised by Mr. Kapp into two classes:—

     I. Core transformers, one core and two sets of coils.
    II. Shell transformers, two cores and one set of coils.

No. I. are those in which the copper coils are spread over the surface
of the iron core enveloping the latter more or less completely; and No.
II. in which the core is spread over the surface of the copper coils
forming a shell over the winding.

[Illustration: FIG. 10.]

The original Goulard and Gibbs secondary generator was of the core
transformer type, it had an open magnetic circuit and cores which
could more or less be inserted into the coils so as to regulate the
electro-motive force of the secondary circuit. The transformers were
constructed with a number of copper disks or washers; these were
placed alternately primary and secondary in a vertical frame, through
the centre of which an iron core was fixed, consisting of a bundle of
straight iron wires. The core was movable in the coil in the manner of
the well-known induction coils, and thereby the electro-motive force
of the secondary current could be adjusted. In their latest design
the coils are circular in plan and rectangular in section and are
surrounded by groups of U-shaped soft iron stampings slipped over from
both sides and held together by two circular cast-iron plates with a
central bolt. The magnetic lines of force pass through the core, in at
one end and out at the other, and are then more or less disseminated
through space; it will thus be seen that the path of the lines lies
partly in iron and partly in air, and, since air has about seven
hundred times more magnetic resistance than iron, it is evident that
the number of lines created with a given current must be considerably
smaller than would be the case if the path of the lines contained iron
only. This constitutes the improvement in the Zippernowsky-Deri-Blathy
system of transformer, which has coils similar to the Goulard, but with
the iron of the core applied in the form of a ring-shaped shell,
surrounding both coils completely. This arrangement can best be
described by comparing it to a Gramme armature, in which the copper and
the iron have changed places. Imagine what is usually the core in an
armature replaced by the primary and secondary coils, and, instead of
the winding of insulated copper wire, wind iron wire around the coils,
and one of these transformers is the result. In consequence of the
lower magnetic resistance of the Class II. transformer, as compared to
that of Class I., the electrical output obtainable with equal weights
of copper and iron appears to be considerably greater in the former
apparatus. Professor Feraris, of Turin, has published some of the
results of comparative experiments made with Classes I. and II. and
finds that the coefficient of induction is 3·6 times as great with the
latter as with the former. There are many varieties of transformers
in the market which closely resemble each other; one of the most
practical is that designed by Kapp and Snell, of which Fig. 10 is an
illustration. U-shaped stampings form the shell and the cores are laid
in the double trough. The cover of these troughs is formed from the
metal removed from the interior of the stampings, and the whole is held
together in a cast-iron frame so arranged as to allow air to circulate
through the core and round the coils. The price of these transformers
is about £4 per indicated horse-power, and the efficiency under the
best conditions, namely, with full load, is, according to Professor
Ayrton, as high as 96 per cent., and when it is doing one quarter of
the full work 89 per cent.


APPLICATION OF TRANSFORMERS.

The installation at the Grosvenor Gallery, London, may be taken to
illustrate Class I. or the practical working of distribution by means
of transformers.

Fig. 11 represents the arrangement of primary and secondary circuits.

An alternating current is sent through the main L L¹, which is a closed
circuit, and a small portion is drawn off wherever there is a secondary
generator or transformer T; these instruments are placed in parallel
between the conductors in the same manner as a glow lamp; neither main
can be called positive or negative, as the current flows backwards and
forwards many times in a second. The house wires M M are joined to the
secondary circuits, and are quite distinct from the main, which they
do not even touch, although sufficiently near to receive an induced
current alternating the same as the primary, but of a much lower
electro-motive force.

[Illustration: FIG. 11.

    D, alternating current dynamo;
    E, continuous current dynamo for exciting;
    L L¹, main primary conductors;
    M M, secondary conductors;
    T T, transformers;
    S¹ S² S³ S⁴ S⁵ S⁶, lamps in parallel.]

The Goulard transformers were used at first, but have been superseded
by others designed by Mr. Ferranti; they are of the No. 2 kind, or
shell type, and have a core of hoop-iron, on which the two coils are
wound; the hoop-iron is then bent over, and the ends joined so as to
enclose the coils. The machinery is fixed in a basement excavated under
the Grosvenor Gallery; the foundations are of massive concrete, in which
stone supports for the engines and dynamos are embedded; the concrete
does not touch the walls of the building, but a space of about 1 foot
is left, which is filled in with clay; and by this simple plan all
vibration of the machinery is isolated from the building. The power
is obtained from two horizontal high-pressure engines, each of 600
indicated horse-power, in addition to the original two horizontal
high-pressure non-condensing engines, each of 35 nominal horse-power,
running at a speed of 55 revolutions per minute, which is maintained
constant by means of a governor directly attached to the expansion
slide-valve. The four engines drive on to a countershaft, which is
cut up into lengths; each section is coupled to a dynamo and exciter
by means of a conical friction-disk clutch; this permits of either
length being started or stopped without interfering with the other. The
speed of each engine is checked by means of a liquid speed-indicator,
designed by the author. Two Ferranti alternating current dynamos,
each capable of maintaining ten thousand lamps, are driven direct,
one dynamo by each length of shafting: they are excited by two
continuous current machines, the circuits from which are joined
to a regulating apparatus, which by altering resistance keeps the
electro-motive force of the large machines proportional to the number
of lamps which are to be maintained. At present hand regulation is
employed, but it is proposed to use automatic regulation, which
will increase the life of the lamps, as they are severely tried
by the variation of the current, which is more noticeable than in
continuous current installations. The current from the machines is at a
potential of 2400 volts, and that from the transformers is 100 volts.
The primary wire which carries this high electro-motive force does not
enter the houses, as the transformers are, as a rule, fixed in the
cellars, and from them the house branch is led in the form of a cable
of fine wires, having a total diameter of 7/16 inch; the lamps, which
are placed in parallel across this cable, are attached to single No. 18
or No. 20 B. W. G. wires in the usual manner. When first established,
the transformers presented an element of danger, in that they, in
common with all induction coils, were also condensers, and therefore
a dangerous shock might be given to any one touching some unguarded
portion of the lighting system. This has been prevented by the simple
plan of connecting one of the terminals of every secondary circuit to
earth, a method which, however, is not to be recommended, as it throws
an additional strain on the insulation of the primary circuit; in fact,
by earthing the secondary the insulation is practically reduced to
one-half. A safety device should be inserted, which would come into
operation on any leakage from primary to secondary, and immediately cut
out the transformer.

The primary-current conductor is led overhead, and still remains an
objectionable feature of the system, although the original trouble
with the neighbouring telephones and telegraphs has been overcome.
The primary circuit is a small carefully insulated cable of high
conductivity copper wire, nineteen strands of No. 15 B. W. G. It weighs
about 1¾ ton per mile, and is suspended, where it crosses the streets,
on a steel bearer whose tensile strength is 1⅕ ton. It is so arranged
according to the droop of the cable that the strain of the bearer never
exceeds 225 lbs., which means that the factor of safety is nearly 12 to
1. Double cut-outs or safety fuses, in many instances of the author’s
design, are placed on each pole of the primary, at the point where
it enters the house, so that, in the case of an excess current, the
mica-foils would fuse, and all connection between that house and the
supply main would cease.

Much credit is due to M. Goulard, who, in spite of great opposition
to the use of his transformer system, initiated the Grosvenor Gallery
installation three years ago. It has developed into not only the
largest and most important central-station in Europe, but, as regards
the transformer system, it supplies more lights than any in the United
States. The original company has been taken over by the London Electric
Supply Corporation, who are putting down plant capable of maintaining
30,000 lights, and are erecting another station at Deptford for 200,000
lights, which will be distributed by means of district transformers
from mains, which it is proposed to run from Deptford through the
Thames Tunnel and the Underground Railways. The electric current is
supplied by meter at the price of 7¼_d._ per Board of Trade Unit, a
price for light equal to gas at about 4_s._ 2_d._ per 1000 cubic feet.

The Eastbourne station is also on the transformer system. An
alternating current dynamo, by Ellwell Parker, maintains a pressure
in the primary circuit of 2000 volts, which is reduced by means of a
Lowrie Hall transformer to a working pressure of 100 volts. There is a
special arrangement for maintaining a constant electro-motive force in
the mains, independent of the number of lights in use. The mains are
carried underground, and have so far given no trouble as regards the
insulation of the high-tension current which passes through them.
The Eastbourne company commenced by lighting the parade only with
arc lamps, but now supply the incandescent light to all parts of the
town, and enjoy the unique position of having obtained power from the
corporation to run the mains in the streets prior to the passing of
the Act of 1882. Another small station has been successfully worked
for the last six years at Brighton; the group system was originally
adopted, the lamps, both arc and incandescent, being placed in
series or multiple series; the high-tension current is led through
overhead wires in a very similar manner to the installation at
Temesvar, Hungary, which is described at page 58, as an example of
multiple series lighting. The extensions at Brighton are to be carried
out on the transformer plan, which will necessitate the running of
separate circuits, the intention of the company, however, being to
gradually convert its whole system of supply to the transformer system.
The Brighton Company has regularly paid dividends to its shareholders
since its formation.

       *       *       *       *       *

On the Continent the Goulard transformer is largely employed.

An important installation at Tours of 3500 lamps has been for some time
successfully working. Another at Tivoli has some additional points
of interest, in that the natural power of a waterfall is applied to
generate electricity. Two turbines constructed by Escher Wyss, of
Zurich, having an available head of 29·75 feet, give 80 horse-power
each, which is employed to drive two Siemens alternating current
dynamos, separately excited by two small continuous current machines.
Two distinct circuits of chromo-bronze naked wire, 3·7 millimetres in
diameter, are run overhead, in the same manner as telegraph wires,
through the town for a total length of about nineteen miles. The street
lamps are fixed alternately on each circuit, so that one-half can be
extinguished at a late hour without interfering with the others, or
having to turn out individual lamps. The number of lamps used in the
streets is two hundred glow lamps of 50 candle-power; also one hundred
and twenty glow lamps of 16 candle-power for the illumination of the
narrower streets. Arc lamps are also employed, as well as a large
reflector lamp, the rays from which are turned on the Temples of Vesta
and Sibilla. A house-to-house system is also being established, and
the company which has put up the work proposes to utilise the falls of
Tivoli in order to transmit 2000 horse-power for lighting purposes in
Rome.

       *       *       *       *       *

The firm of Ganz, of Budapest, who are the manufacturers of the
Zippernowsky-Deri-Blathy system of transformers, have a similar
installation completed in order to light a portion of Lucerne. The
water power of Thorenburg 3·1 miles off, works the turbines, which
drive two self-exciting alternating current dynamos of the Ganz type,
similar to those shown at the Vienna Exhibition in 1884. The primary
current of 38 ampères, at an electro-motive force of 1800 volts, is led
by four uncovered wires, each six millimetres in diameter, to the
first station, which is 2·4 kilometres distant; here 1500 watts are
taken off, and at 2·3 kilometres further 7000 watts are utilised in
two of the hotels at Lucerne. A large installation on the same system
has been put down in Rome, and several Continental cities are adopting
this method of supplying electric light by small overhead wires. An
advantage claimed by the Zippernowsky system is the method of keeping
the strength of the magnetic field of the dynamos in accordance with
the external demand for current. The regulating apparatus employed
consists of a small transformer, the primary coil of which is traversed
by the whole, or by a proportionate part, of the main circuit, while
the secondary coil is inserted into the exciting circuit. Thus, if
the main current increases, the exciting current induced in the two
armature coils of the dynamo is reinforced by the inductive action of
the regulating transformer; and the field of the dynamo is strengthened
when more current is required. The opposite takes place when, through
the extinction of lamps on the external circuit, the demand for current
becomes less. In an experiment made with the transformers, which
supply some five hundred electric lamps for the Teatro dal Verone
and adjoining houses at Milan from the central electrical station
three-quarters of a mile away, the main current was often found to vary
from one ampère to thirty-five ampères; it was stated that no variation
in the service pressure could be detected, and the lamps burnt with
equal brightness whatever the number in use. In the experiments at the
Teatro dal Verone each transformer worked its own independent circuit
of lamps; but, if the conditions of the different circuits were alike,
they could be coupled up together in any manner desired, and thus a
group of transformers could become a centre of distribution.


THE WESTINGHOUSE SYSTEM.

The alternating current system of the Westinghouse Company has come
to the front in the United States with extraordinary rapidity, and,
although it is not three years since the first plant was erected, at
the present time over 190,000 incandescent lamps are operated from a
number of central-stations. The fundamental principles of the Goulard
system have been retained in the Westinghouse converter; but the manner
in which these principles are applied has been greatly modified, while
most of the details have undergone a radical change at the hands of the
engineers and electricians whose researches have been utilised by the
Westinghouse Company. The form of converter as now designed consists of
a number of thin sheet-iron plates, shaped like the letter =E=, they
are slipped alternately from opposite directions over the primary and
secondary coils, which are disposed side by side; the inductive core
is, therefore, composed of a mass of detached plates insulated from
each other by paper, and forming a discontinuous magnetic circuit.
In order to protect the converter from mechanical injury as well as
dampness, and also to avoid the possibility of contact with wires
carrying currents of high potential, it is enclosed in a cast-iron case
or box, made in two parts and adapted to be secured to any convenient
support. Fig. 12 is a transverse vertical section of such a converter
box, with the converter in position. The terminals of the primary
coil, P, of the converter are led into the compartment D¹, and the
terminals of the secondary coil into D². The terminals are secured
to bolts or couplings, _f f_, mounted upon insulating plates, _e_¹
and _e_². Fusible mica-foils, _g_, and switch plates, _h_ and _i_,
with plugs _k_, are provided for protecting and disconnecting the
circuits. The open front of the compartments D¹ and D² are closed by
glass plates, T, which permit inspection of the connections without
entering the box. The converter box occupies little space, and may
be placed in any convenient situation in or about the premises to be
lighted, much the same as a gas-meter. The practice where overhead
conductors are employed, is to mount the converter box on a pole in
the vicinity of the premises to be lighted, as shown by Fig. 13, and
thus it is only necessary to lead the secondary or low potential wires
into the building, the high potential wires remaining in an accessible
position upon the pole. Fig. 14 is a view of North Street, Pittsfield,
Massachusetts, engraved from a photograph, and shows a very neat form
of tubular pole with its converter box on top. This arrangement is used
throughout the city, and is a great improvement on the ordinary form
of telegraph poles which so greatly disfigure American cities, and are
really the most objectionable feature of the overhead wire system.

[Illustration: Fig. 12.]

[Illustration: FIG. 13.]

[Illustration: FIG. 14.

_To face page 37._]

The potential ordinarily employed in the main circuits of the
Westinghouse installations is about 1000 volts, and that in the lamp
circuits 50 volts, the ratio of conversion, therefore, being as 20
to 1; the dynamos are manufactured, as a rule, in three sizes, No. 1
for 650, 16 candle-power lamps; Nos. 2 and 3 for respectively 1300
and 2500 lamps. The converters are also made in three ordinary sizes
to supply 20, 30, and 40 lamps of 16 candle-power each. A 40-light
converter contains about 85 pounds of iron and 25 pounds of copper,
so that the total weight of metal is less than 3 pounds per lamp;
the electrical efficiency of the converter is said to exceed 95 per
cent. when the potential is reduced from 1000 volts in the primary to
50 in the secondary. “It is claimed that the trifling loss of energy
in conversion from high to low potential at the point of consumption
is made up for by gain at other points, especially in the increased
efficiency of the lamps, so that an alternating current plant may be
counted on to give 10-16 candle-power lamps per indicated horse-power,
as against 7 with the direct system;” the comparative gain is doubtful,
but by using 50 instead of 100 volts the life of the lamps is
increased, the former having a much stronger filament and consequently
a longer life.


ELECTRIC MOTORS.

Having slightly diverged from the original lines by describing a system
which is at present not introduced into Europe, a few remarks on the
subject of electric motors may not be inappropriate, as they are almost
universally worked in the United States, from the installation which
supplies electric light. There is a considerable profit to the electric
company if electric power is taken in the district, the wires conveying
the lighting current are thus economically employed during the day. In
the diagram, Fig. 15, which represents a district at Boston, the curve
on the right principally represents the demand for power which takes
place between the hours of 8 A.M. and 3 P.M. A circular was addressed
to all the leading electric companies in America a short time ago,
asking if they supplied power as well as light, also for what purposes
it was used.

Answers were received from 56 companies, who stated that the motors
were employed for:—driving ventilator fans, collar-and-cuff machines,
printing-presses, various apparatus in repair-shops, sewing-machines,
coffee-mills, gun-shop tools, sausage-machines, elevators, lathes,
pumps, saws, ice-cream freezers, organ-bellows, and washing-machines.
The size of motors varied from one-eighth to 15 horse-power; 26
companies have supplied motors from arc light circuits, 14 from arc and
incandescent, and 16 from incandescent circuits alone. The motors are
principally owned by the subscribers, and are charged for at a rate
varying from £3 to £15 per horse-power per month. The motor business
is still in its infancy, but is cited to show how Electric Power can
supplant the steam-engine, especially for those purposes in which the
power required is small and complete control is desirable.

[Illustration: FIG. 15.]




CLASS II.

THE EDISON PARALLEL SYSTEM, WITH CONTINUOUS CURRENT.


It will be found, on examining Appendix II., that in European stations
by far the larger number of lamps are maintained from installations
employing the Edison system; the Ferranti plan of using transformers
comes next, closely followed by Goulard and Zippernowsky; the
distribution with secondary batteries follows, and the high-tension
multiple series comes last.

[Illustration: FIG. 16.]

The Edison system has frequently been discussed, in connection with
small installations, but in magnitude the stations in Berlin and in
Milan exceed anything that has been started here with continuous
current.

Before describing the central electric light station at the former
city, it may be well to recall to mind that the Edison plan is the
combination of a number of machines which pump electricity into a
network of feeders, mains, and conductors, the lamps being placed in
parallel circuit, as shown at L _l_, Fig. 16, and maintained at a
constant potential of 110 volts.

[Illustration: FIG. 17.]

M M′ are the flow and return mains, the dynamos bridging them across at
one end. If the mains were very long, those near to the dynamos would
be exhausting the supply, and the lamps at the remote end would not get
the full pressure. A system of feeders has been devised so that each
lamp, no matter where it may be, shall have approximately the full 110
volts working through it. Fig. 17 shows a long circuit consisting of
two branch mains bridged by a large number of lamps, _l l_, and D D are
the dynamos at the central-station. Series of feeders, _f f′_, have to
be taken from the dynamo mains and fed direct into the branch mains
at various points, _d d′_, _b b′_, _c c′_, in order to distribute the
electrical pressure equally.


THE THREE-WIRE SYSTEM.

The ordinary parallel system is undoubtedly suitable for small
installations; but when the area to be lighted is extensive, it is
impossible to proportion the mains, with a view to economy in the cost
of copper, without sacrificing energy wasted in heating the conductors.

In Figs. 16, 17, the lamps are shown in simple parallel; but if two
dynamos are connected together, and a main wire is run from each of
their two extreme terminals and a third wire from the branch connecting
the two machines, we have what is known as the three-wire system,
which was invented by Edison in America, and Hopkinson in England,
almost simultaneously. Although by using the third wire there is a
saving in copper over the parallel plan, the maximum gain is not more
than 25 per cent., under the best conditions; when the district to be
illuminated is not more than 400 to 600 yards from the central-station,
the three-wire system answers well, but as soon as this distance is
exceeded the cost of the mains begins to mount up at a most alarming
rate. Although there are many Edison installations in the United States
on this system and a few on the Continent, it has only been used here
in a few instances for factory lighting.


THE EDISON SYSTEM AT MILAN.

The Santa Radegonda station at Milan is at the present moment the
second largest Edison station in Europe. The building, which was
formerly a theatre, is well adapted for the work required; the dynamos
and engines are fixed in a deep basement, while the boilers are a few
feet above the street level, the upper floors being used as stores and
testing-rooms. The dynamos, eight in number, are of the old Edison
type, with horizontal magnets; seven of these machines are connected to
the feeders which supply the mains, and these cover the district to be
lighted on the Edison network system. The motive power is furnished by
six Armington-Sims, and two Porter-Allen engines, each connected direct
to the armature of a dynamo, the speed being maintained at the uniform
rate of 350 revolutions per minute, except in the case of the spare
engine and dynamo, which is kept turning slowly, ready to be switched
on should occasion demand. The starting or cutting-out of circuit of
these large machines requires some care. In the first place, to start,
it is necessary to insert resistance into the shunt circuit of the
dynamo, which is done by a switch; but to throw 150 horse-power into
the main circuit would be dangerous to the lamps, so that the current
is first sent into a bank of one thousand lamps used as a resistance,
and these are cut out step by step; similar care is taken when a
machine is stopped. To control the electro-motive force, which varies
greatly from time to time, hand regulation is used during the day, with
the help of the Edison tell-tale, consisting of two lamps, a red and
white one, which light up when the current is high or low; but when the
night service comes on, as it may happen that two thousand lamps may be
turned out at once, an attendant has to carefully watch the electric
regulator, and be ready to insert resistance into the field-magnet
circuits by moving a wheel connected by a shaft and bevel-gear to a
system of commutators. The principal difficulty to be overcome, in
an installation where the current is distributed over a large area,
is the regulation of the electro-motive force at the various points,
as at Milan; there are no return galvanometer wires, which are now
used in both the two and the three-wire Edison systems in the United
States. The plan devised by the company’s electrician at Milan is very
ingenious, and enables the pressure at the ends of the various feeders
to be kept practically the same, although they are of different lengths
and sectional area. In the first place, resistance was added to each
feeder to equalise the resistance in each conductor; and, in order to
provide for the varying amount of current the feeder has to supply, a
peculiar form of commutator, having a guillotine-shaped contact-piece,
was inserted in the circuit. By moving this, suitable resistance is
inserted or cut out, and the attendant, having a series of numbers, has
only to set this instrument to the number shown by the ampère meter. By
far the largest amount of current is drawn off for the lighting of the
Scala Theatre, the stage-lighting alone taking more than one thousand
lights: if these were all turned on suddenly, the other lights in the
district would be dimmed; to obviate this, auxiliary feeders have been
run, which are used only when any great increase is expected;
commutators similar to those referred to above also regulate these
feeders without any special attention. The pressure at any point in the
system is by this means easily controlled, and affords an illustration
of what is perhaps not the most economical, but is found to be the most
practicable, way of maintaining a constant potential in a district
where the amount of output of current is suddenly doubled. Fig. 18 is a
plan of the network system of conductors laid through a large portion
of the city; the conductors are in outward appearance similar to
gas-pipes, the current passing through semicircular bars of copper,
embedded both for the flow and return in the same iron tube, which is
laid underground in a shallow trench. The house-supply is drawn from
the mains, and these are connected to the feeders by means of ordinary
junction-boxes, which each contain a fusible cut-out. The bridge-boxes
allow of expansion of the line, and have connections for testing
purposes. The insulation is extremely good, mainly on account of the
favourable nature of the ground, which is chiefly gravel; no trouble
has been experienced with leakage, nor has the service ever been
interrupted. The cut-outs are of an improved Edison form, but have the
disadvantage attending all lead plugs where the current is great, in
that, to guard against accidental melting due to the heating effect of
the current, the sectional area of the lead has to be much larger than
would be otherwise necessary. In fact, these cut-outs will protect the
cable against a bad short circuit, but nothing else.

[Illustration: FIG. 18.]

In addition to the glow lamps, eighty arc lamps are worked in
derivation, two in series; most of these lamps require 45 volts,
to which 10 per cent. of idle resistance is added, constituting a
total loss of current which is extremely low for a combined arc and
incandescent system of lighting. The service commenced in 1882 with
a little over one hundred lamps, and at present there are over ten
thousand glow lamps, and two hundred arc lamps are in use. At first the
new enterprise had to struggle against very great difficulties; not
only the technical difficulties of distribution by means of a network
of feeders and mains had to be overcome, but also those arising from
the prejudices of consumers and the competition of the gas company,
who tried to deter consumers from introducing electric light into
their houses. One of these means consisted in offering to the private
consumers, resident in the district which was threatened by competition
with electricity, an agreement by which the gas company bound itself to
supply gas at 5_s._ 8½_d._ per 1000 cubic feet, instead of 7_s._ 7_d._
as charged hitherto; and even now those inside the “charmed circle” of
the electric light conductors get their gas cheaper than the public
outside. One of the reasons which accelerated the adoption of electric
light was the introduction of the Edison meter, in consequence of which
consumers could be charged exactly for the amount of light they had
received, and were relieved from paying a lump sum according to the
number of lamps fixed, which was customary in the early days of the
company. The prices at which the company now provides light, at all
hours of the day and night, are as under:—

                       Installation      Charge per
    Type of Lamp.    charge per lamp.    lamp·hour.
                           _s._              _d._
    10-candle               18              0·26
    16-  ”                  28              0·40
    32-  ”                  56              0·80

that is, a little over ½_d._ per ampère-hour; the 10-candle lamps
requiring 0·5, the 16-candle lamps 0·75, and the 32-candle lamps 1·5
ampère.

The company lends meters for 50, 100, and 150 lamps, at an annual
rent of 4_s._ 10_d._, 7_s._ 3_d._, and 9_s._ 7_d._ respectively, and
replaces, without charge to the consumer, any lamp the filament of
which has broken, but it does not replace lamps where the glass is
broken. For arc lamps requiring 9 to 10 ampères, an annual rent of £2
must be paid for the lamp itself, and a charge of a little over ½_d._
per hour for every ampère-hour. The carbons are charged for at 1_d._
per pair, lasting for about seven hours. Now that the installation has
been in use for several years, and that the company has arrived at a
very accurate estimate of the time during which an average consumer
requires the light—about one thousand six hundred lamp-hours per
annum—it proposes to simplify the method of charging large consumers,
by omitting the initial charge of each lamp, and, instead, to charge
0·6_d._ for each 16-candle lamp-hour.

The Edison meters are based on the electrolytic action of a small
fraction of the current which passes through the meter. They are cells,
with rectangular zinc plates immersed in a solution of sulphate of zinc
of 1·054 density, the distance between the plates being a little over ¼
inch. The proportion of the current which passes through the meter to
that which passes directly into the consumer’s house is 1 to 973. The
resistance of the shunt circuit is 9·75 ohms, made up as follows: cell,
1·75 ohm; metallic portion, 8 ohms. The resistance of the metallic
portion rises with the temperature, whereas that of the cells falls
with a rising temperature; and in this manner the small variations of
resistance which might take place in the cell are counter-balanced
by the equally small variations in the resistance of the metallic
portion. A complete meter consists of two similar-sized cells of the
same resistance, placed in series. The object of employing two cells
is, that when little current is passing, as in the summer months, one
cell alone is used, and when the consumption is sufficiently large both
cells are employed, and the mean between the two indications is taken
as the basis for calculation in number of ampère-hours. The quantity of
electricity passed through the cell is calculated by the loss of weight
which has taken place in the positive plate. An employé of the society
visits every meter monthly, taking away the old cells and substituting
others freshly constructed. A book is kept in which the weights of the
new plates and those of the returned plates are entered, and on the
basis of these entries the accounts are made up. The largest plates are
those in the 100-light meter, and are intended for a maximum current
of 75 ampères in the main circuit; they are 6 inches long by 2 inches
wide. In cases where a larger amount of current is taken, the capacity
of the 100-light meter is increased by joining two or more copper
strips across the terminals of the cells. The weak point of the system
is the removal of the cells, which leaves the adjustment of the account
to be paid entirely in the hands of the Electric-Light Company; in
spite of this drawback, it is stated that there has not been a single
complaint from consumers during the four years in which the meter
system has been in use.


_Discovery of Faults._

It is evident that in so extensive a system of lighting a short circuit
now and then between the lamp wires and the earth cannot altogether be
avoided. Many of the lamps have been fitted to existing gas fittings,
and are beyond the daily supervision of the company’s officers; the
faulty place is often not easily accessible, so the first step taken is
to discover on which of the two circuits the trouble has occurred. This
is done at the station by joining two 16-candle lamps in series across
the main conductors and the point of junction between the two lamps is
connected to earth by a stout wire. As long as both circuits (positive
and negative) are perfectly insulated from earth no current flows
through this middle wire, and both lamps remain hardly incandescent;
but, if one of the circuits should be in connection with the earth, the
lamp which is joined on the other circuit will brighten up, because the
potential of the middle wire and that of the faulty circuit are both
zero, and consequently the lamp between the middle wire and the sound
circuit receives the full pressure of 110 volts. To localise the fault,
contact is made between the earth and the sound circuit by means of a
fusible plug of known melting point, say for a thirty-lamp supply. If
the fault is on a portion of the external circuit, supplying less than
thirty lamps, its fusible plug will melt as soon as the sound main is
put to earth. If, however, the fault is on a portion supplying more
than thirty lamps, the fusible plug which has been inserted at the
station between the sound main and the earth will melt instead. A
series of fusible plugs are thus tried, increasing in melting capacity
until one is found that does not go: in this case, the other plug on
the faulty portion has melted, and the consumer’s lamps on that branch
are extinguished; the position of the fault is thus localised, and
the company proceed to remedy the defect without interfering in the
slightest degree with the rest of their system.


THE ELECTRIC LIGHTING OF BERLIN.

The Edison system is also employed at Berlin, in fact the Deutscher
Edison Gesellschaft have at the present time a monopoly of the supply
of the city from three large central-stations, each of which serves
the area in their immediate neighbourhood. The mains differ from those
used at Milan in that stranded highly insulated cables, protected
with steel wire on the outside, are laid under the pavement in every
street throughout the district. With the exception of the Leipziger
strasse and Unter den Linden, which are lit with arc lamps suspended
from chains running between cast-iron poles 24 ft. high, about 100 to
250 ft. apart, gas is used for the street lighting, and electricity
for the interior illumination of many public buildings and private
houses; there are also a good many arc lights outside the shops and
restaurants. The mains are on the Edison network system, the area of
copper being such, that when all the lamps are on there is a loss of
energy of 25 per cent.; but this does not occur on an average for more
than half an hour a day. No sole concession is given to the company,
who simply have the right to take up the pavement and cross streets,
and for this permission they are bound to furnish any consumer in
the district with a constant supply of electricity at the following
charges:—

     10-candle lamps 2·5 pf., about 0·29 _d._ per hour.
     16-      ”      4·0        ”   0·48       ”
     32-      ”      8·0        ”   0·96       ”
     50-      ”     12·5        ”   1·50       ”
    100-      ”       25        ”   3·00       ”

In addition to this an installation fee of 6_s._ per lamp is charged,
which includes one lamp.

Meters are charged as follows:—

                             _£   s.   d._
     10- to 16-candle-power   0   16   0 per annum.
     25-    ”       ”         1    0   0     ”
     50-    ”       ”         1   10   0     ”
    100-    ”       ”         2    0   0     ”

A discount is allowed off this meter charge, varying with the number of
hours the light is used in the year.

The cost of gas is about 4_s._ 9_d._ per 1,000 cubic feet, so the
electric light is slightly the dearer illuminant.

The Aron meter, Fig. 19, is usually employed as the recorder of the
electricity consumed. It consists of two pendulums, controlling two
distinct clockwork gears. One oscillates at a regular speed, but the
other has a permanent magnet, instead of a weight, and is variable in
speed. The entire current passes through the solenoid, which is
underneath the pendulum, with the magnet; the difference in speed
between the standard and variable clocks is given in direct
ampère-hours by a counter-gearing similar to the index of a gas-meter.
An electro-magnet starts each pendulum when the current begins to flow,
and immediately it ceases, two detents come into operation and hold the
pendulums stationary.

[Illustration: FIG. 19.]




CLASS III.

THE SERIES SYSTEM OF DISTRIBUTION.


This method dates back to the introduction of the incandescent light,
and, although it has been frequently demonstrated that a small current
of high potential could be employed to work incandescent lamps, the
series system has never been installed on a commercial scale, and is
confined to arc lighting. In the United States the usual pressure for
arc lighting is 2,000 volts, and it is not an uncommon occurrence to
have forty arc lamps in series upon a line over 10 miles in length,
carrying a current of 10 ampères. To economically use this high
pressure for glow lamps in series, they must be of such design as to
enable the whole of the current to be passed through them without
injury. The filament of an ordinary high-resistance glow lamp would
be immediately destroyed, so that low-resistance lamps, having a much
larger sectional area, must be employed. The Bernstein or the Cruto
lamp, which can be made to have a “hot” resistance of about 0·7 ohm,
and requires a current of 9·75 ampères, could be used, and the current
might be economically brought from a great distance. Mr. Bernstein
calculates that it would be possible to operate 6,000 of these 7-volt
lamps from twenty dynamos, each giving a current of 10 ampères at
a potential of 2,000 volts, and still have a margin for loss of
current in the leads. An economical feature of this scheme is the
easy way in which power could be saved when only comparatively few
lights were required; for instance, in the daytime all the circuits
could be looped together and fed by one dynamo, and, as the number of
lights increased, so other machines could be switched in by having
an auxiliary bank of lamps as a resistance. From the central-station
twenty pairs of carefully insulated copper wires, say of No. 6 B. W.
G., would lead to the houses; and, as a good-sized ordinary house takes
on an average twenty lights, the conductor would pass through fifteen
houses before it returned to the station. It is in the house that the
practical difficulty commences, as in this series system the circuit
must never be opened, so that the switches and safety appliances must
be such that, whatever happens, there must remain some path for the
current, otherwise all the lights on that particular circuit would be
extinguished. Mr. Bernstein gives the designation of “short closed” if
the current goes through the switch-lever, and “long closed” if the
current is led through the lamps or other electrical devices.

[Illustration: FIG. 20.]

Fig. 20 is a diagram of the lamps in any building. The street main, M,
enters at the main switch, S, and continues from switch to switch, S¹
S¹, and returns to S before it leaves. It is necessary, to guard
against any possible extinction, to construct all the switches so that
it would be impossible to move the lever without a lamp was lighted;
and, should the lamp give out, an equivalent resistance must be
automatically inserted. These details have been investigated by Mr.
Alexander Bernstein, who has designed a complete system for “series”
lighting, and claims for it special economical advantages. It is,
however, very doubtful if this plan can be recommended for adoption
in private houses; but in public lighting, or in large establishments
where an electrician could be kept to look after the fittings and
the insulation of the conductors, there should be no more danger, in
introducing the high-tension continuous current of 2,000 volts, than
there is at present with the 100-volt alternating current, and the
relative saving in weight of conductors would be an important item.

Installations on this method have been erected at Messrs. Brunner and
Mond’s alkali works, and in several large factories in the United
States where lights had to be distributed over a considerable area; the
system has not, however, come into favour for central-station work.




CLASS IV.

THE MULTIPLE SERIES SYSTEM.


This method of using a high-tension current has already been referred
to in connection with house-to-house lighting at Brighton, it was first
employed for the street lighting of Chesterfield by the Brush Company.
The electric lighting of the town of Temesvar, in Hungary, is on a far
larger scale, and has, from November 1884, successfully superseded a
combination of gas for the more important streets, and petroleum for
the outlying ones, the total cost of which was 26,480 florins per
annum. A twenty-four years’ concession was given to the International
Electric Company, the plant remaining their property at the expiration
of the term, subject to purchase by the municipality at their own
valuation. The public lighting is stipulated to be effected by means of
731 glow lamps of the intensity of 16 candle-power; but the option is
given to the company of switching out a fixed proportion of these lamps
at 11.30 P.M., or of leaving the whole number in operation
with their light-intensity reduced from 16 to 8 candle-power from 11.30
P.M. till dawn. The total number of lighting hours per annum
is 3,597½ for the lamps which are in operation from dusk until dawn,
and 1,816 for those which are extinguished at 11.30 P.M. The
price fixed in the concession for public lighting is 1·5 kreutzer per
16 candle-power lamp per hour, equal to 53 florins 95 kreutzers per
lamp per annum of 3,597½ hours, or 27 florins 24 kreutzers per lamp
per annum of 1,816 hours. The company has found it more convenient
to exercise the option reserved to it, of keeping all the 731 lamps
in operation from dusk till dawn, reducing their light-intensity to
8 candles after 11.30 P.M.; and the municipality has agreed
to pay a round sum of 29,000 florins (£2,416 13_s._ 4_d._) per annum
for this lighting, and 41·95 florins (£3 10_s._) per annum for each
additional lamp worked in the same way. Comparing these figures with
what precedes, it will be found that the electric lighting of the
streets now in operation costs 2,520 florins more than it did on
the former plan of combined lighting, partly by gas and partly by
petroleum. On the other hand, the streets are lighted throughout with
16 candle-power lamps from dusk until 11.30 P.M., and with 8
candle-power lamps from 11.30 P.M. until dawn. For electric
light supplied to private consumers the concession fixes the price at
1·81 kreutzers per 16 candle-power lamp per hour, or 0·1131 kreutzers
per candle per hour, with the right to charge 15 per cent. more for
lamps of less intensity than 16 candles. In all these prices the
renewal by the company of lamps failing from legitimate wear is
included.

[Illustration: FIG. 21.

MULTIPLE SERIES LIGHTING. TEMESVAR.]

One central generating station has been provided for the whole town,
from which at present four distinct circuits have been laid, each fed
by a separate dynamo. The street lamps are connected up in “multiple
series,” that is to say, in groups placed in series on the circuit, the
lamps in each group being connected up in parallel.

Fig. 21 shows the arrangement diagrammatically. Each group consists
of eight lamps in parallel; at present three of the circuits have
twenty-four groups in series, and the fourth circuit has twenty-three
groups in series, giving a total of ninety-five groups, comprising 760
lamps, of which 731 are public lamps and 29 are used at the central
station. To meet the risk of interruption in any circuit through
the failure of individual lamps, an automatic switch is arranged so
as to put in a reserve lamp, in the event of a whole group being
interrupted. Another self-acting device will short circuit the whole
group, so that the other groups in the circuit will be unaffected. The
automatic lamp-switch is contained, together with the reserve lamp,
in the lantern, and the automatic group cut-out consists simply of an
electro-magnet with a coil of high-resistance connected up in parallel
with the group of lamps it protects. These appliances have been found
to work well. The main conductors are formed of insulated single
copper wire, 4·6 millimetres in diameter; they are carried overhead on
porcelain insulators, fixed to telegraph posts or to wooden arms let
into the walls of houses; the resistance of this conductor is about 1·1
ohm per kilometre. The glow lamps are placed in reflectors at an angle
of about 45° from the vertical, and are carried on brackets either
fixed to the walls or on special cast-iron posts. Fig. 22 shows the
details of street bracket and reflector with automatic lamp-switch and
lamps in place. The brackets are for the most part fixed to the walls
of houses or to painted wooden posts.

[Illustration: FIG. 22.

LAMP BRACKET.]

The under side of the reflector, which is made of enamelled iron
disposed in the form of a flat inverted cone, reflects the upward
rays from the lamp and causes the extreme ones to strike the ground
at a distance of about 50 metres from the foot of the lamp-post. The
increase of lighting effect in the streets due to those reflectors
is very marked. The upper part of the reflector serves the purpose
of a case and weather protector for the automatic lamp-switch which
is inserted from the top, and the lower end of which is fitted with
copper hooks to which the two lamps are fixed. The glow lamps are
fitted with holders of a type designed by the engineer, which provide
the lamp terminals with large and strong eyes affording considerable
contact surface and adapted for hooking on direct to 2·5 mm. copper
wire, the ends of which have merely to be bent into a suitable form for
maintaining the lamp in any required position. These lamps are of an
improved Lane Fox type, manufactured by the Electrical Company, at
their works in Vienna. Although originally intended for 16 candle-power
lamps they have so far been worked at 18 candle-power, taking 53·618
volts and about 1·183 ampères, which is equivalent to 3·522 watts per
candle-power, or about 211 candles per horse-power. The current is
maintained at 10 ampères, and the potential between independent groups
of lamps is 53·6 volts. The aggregate energy lost, in overcoming the
resistance of the main leads, switches and cut-outs, is 12·8 per cent,
of the total electrical energy generated at the central-station—a
very satisfactory result on a system of over 37 miles of streets. The
electro-motive force in the conductors is about 1,400 volts, which is
below the normal capacity of a Brush machine, thus allowing more lamps
to be operated from the four machines. The machinery is driven by a
300 horse-power horizontal compound-condensing tandem steam-engine,
running at the normal speed of 100 revolutions per minute. During the
first 1,200 hours of lighting, only three lamps out of 760 failed, and
one of these had been broken maliciously. The engineering arrangements
are due to Mr. C. F. de Kierskowski Steuart, M. Inst. C.E., the
various difficulties incidental to a novel work having been surmounted
with experienced workmen. Although the system at Temesvar has more
complicated arrangements than are now required if secondary generators
are used, it has shown that it is quite practicable to light all the
streets in a town by electricity; also it has enabled a comparison to be
made between the useful effect obtainable from arc and from glow
lamps. Each group of glow lamps was found to absorb practically the
same energy as one arc lamp of from 800 to 1,000 candle-power, and
ninety-one or ninety-two of these could have been run with the same
expenditure of power as 731 glow lamps. The eight glow lamps forming
one group are in many cases scattered in different streets, often quite
out of sight of each other. Under such circumstances, the substitution
of one light centre, however powerful, for every eight could only be
done by leaving many spots in complete darkness. To give a usefully
diffused light by means of arc lamps, their number would have to be
considerably greater than ninety-two, or, in other words, the standard
of street lighting would have to be raised, and for this the town was
not prepared to pay.

The business has now passed into the hands of the Anglo-American
Corporation of London, who are extending the installation by placing
alternating current dynamos at the station to work transformers for
the supply of houses so as to utilise the original plant for street
lighting only, as, even with the advanced knowledge of the present day,
it is doubtful whether for this purpose a more economical system could
be employed.




CLASS V.

THE DISTRIBUTION WITH SECONDARY BATTERIES, OR THE BATTERY TRANSFORMER
SYSTEM.


Mr. Lane Fox was the first to put forward a complete system of
electrical supply on this plan, Fig. 23.

[Illustration: FIG. 23.

    G Generating station.   A Accumulators (secondary batteries).
    R Returns.              M Mains or conductors.
    L Lamps.                X Meters.
]

The system is discussed by him as follows:[4]—

“The chief points of the system is the use of a generator in a central
position, from one pole of which insulated conductors or mains are led
to the several points where the electric energy is to be utilised,
being branched and sub-branched as much as required, and thence back
to the other pole of the generator by an uninsulated conductor, such
as the gas or water pipes. At certain points, storage or secondary
batteries are set up in connection, on one hand, with the mains,
sub-mains, and branches, as the exigencies of the case may require,
and, on the other, with the return conductor.”

[4] Hedges on the Supply of Electricity by Local Authorities.
Proceedings of Association of Municipal and Sanitary Engineers and
Surveyors, vol. ix. (1882-83), p. 159.

“The combination of generators, circuit and storage batteries is such,
that when the current from the generators falls below the demands made
on it from the various outlets to the mains at which its energy is
utilised, the deficiency is made up from the storage batteries, which
act in unison to supply the requisite quantity of energy. On the other
hand, when the current from the generator exceeds in point of quantity
the demands upon it at the various outlets, the excess goes to charge
the storage batteries and to create a reserve to be called upon in case
of need.”

The objection to the system which prevented it being put in practical
operation was the use of the earth as a return conductor. Besides the
great danger of short circuit, the gas and the water pipes, which
are so thickly laid in most cities, would conduct the current and
interrupt telegraphic and telephonic communication. The experiment of
using storage batteries as reservoirs, from which a constant supply of
electricity could be drawn as required, was tried on a considerable
scale at Colchester, where a large installation was started in 1884,
secondary batteries being placed in favourable positions, and charged
by a high-tension current. The plan adopted is shown by Fig. 24.

[Illustration: FIG. 24.

A is a meter in charging circuit; B, the batteries or accumulators; L,
lamps in parallel on low-pressure service main.]

The dynamos were two of the Brush type, each dynamo giving a current
of 9·5 ampères, with an electro-motive force of 1,800 volts, when
rotated at a speed of 700 revolutions per minute. They were driven by
a semi-portable engine indicating 90 horse-power. The dynamos were
coupled in parallel circuit for quantity, and excited by a small
machine giving 10 ampères. The current was led some distance by a
seven-strand 19 B. W. G. cable to the batteries, which were charged in
series, the 60-volt lamps being placed in parallel on separate mains
connected to the batteries. The danger of introducing a high-tension
current of 1,800 volts into the houses was obviated by a rocking-switch
worked automatically, so as to throw the batteries out of the charging
circuit. The operation was accomplished by means of a master cell M,
C, Fig. 24, similar to the others, but fitted with an arrangement
to collect the gas evolved, which extended a diaphragm attached to
a make-and-break arrangement which worked the rocking-switch. The
Colchester installation did not turn out commercially successful, and
has been abandoned; but the experiment has been valuable, and there
is little doubt that, with simplification of details, a high-tension
charging current could be led from a dynamo fixed in any convenient
site where power is available; also in very crowded districts the
batteries could be placed in cellars and be drawn from as reservoirs,
so as to furnish a constant supply of electricity.

[Illustration: FIG. 25. _To face page 69._]

The Kensington Court installation has been previously quoted as an
example of what promises to be one of the most successful methods
of distributing a constant supply of electricity through a large
area, a description of the station may therefore be interesting. The
accompanying elevation, Fig. 25,[5] shows the unpretending design
of the building, and the very compact arrangement of the generating
machinery and batteries. When the illustration was made the plant
consisted of one Willan’s single-crank triple-expansion engine in
combination with a Crompton dynamo provided with vertical inverted
single magnets, the output being 250 ampères at 140 volts when running
at 500 revolutions per minute, the steam pressure being 160 lbs. on the
square inch. A complete duplicate plant has already been installed, and
three more sets of engines and dynamos are shortly to be erected. The
draught from the boiler is led downwards by an underground flue, with
the object of economising the very limited space as much as possible.
As a rule, the dynamo and accumulators are used in parallel, the
current enters and leaves the regulating cells by the same contact,
in other words, there is only one switch which serves for charging
and discharging the batteries. This switch has nine contacts, so as
to give nine degrees of regulation of the light; when the dynamo and
accumulators are working together, the lights are parallel with either
41, 42, or 43 cells, according to the amount of charge in the cells and
current required, while, when the dynamo is out of circuit, the lights
are worked off, 50, 51, 52, or 53 cells. The current passes through the
usual measuring instruments, and each main conductor is protected by
safety fuses mounted in a Hedges duplex cut-out. The accumulators are
of the Planté type, but instead of being plain lead are sawn out of
ingots which are cast porous on the Howell process. Each cell contains
35 plates, 8 in. × 8 in., and, as each plate when fully formed is said
to be capable of yielding five ampère-hours per pound of lead, the cell
has about 600 ampère-hours total capacity. In the event of a serious
breakdown the whole of the work would fall on the accumulators, which
could furnish a steady current for perhaps an hour or more; and herein
lies the novelty of the arrangement. For the first time we have an
accumulator put in not only as a fly-wheel to the whole system and
to give the advantage of supplying current throughout the day and
the small hours when the engine is not running, but also to act as
an actual reserve. The routine is as follows:—the dynamo will start
charging the accumulators a few hours before dusk; for a short time
after lighting hours commence, the dynamo alone will supply sufficient
current, but later on the demand will gain on the dynamo, and a certain
portion of the discharge will be from the accumulators. At eleven
o’clock at night the engine will be stopped and the accumulators will
alone supply the demand for the rest of the night. In the small area
occupied by the station there is ample room for a plant of six times
the present capacity, and it is intended to erect sub-distributing
stations at points at the outskirts of the district where accumulators
to act as transformers will be fixed, which will be charged by a
special main with a current of 500 volts, the outgoing wires from the
sub-station taking electricity at the usual E.M.F pressure for
incandescent lamps in houses of 100 volts.

[5] From _Industries_.

Thirteen candle lamps are used in the district, having been found to be
more convenient than 16 or 20 candle-power, the 13 candle is obtained
for 36 watts, or 2·75 watts per candle. The price charged to consumers
is 8_d._ per Board of Trade unit, or equivalent to gas at about 4_s._
7_d._ the 1,000 cubic feet. Meters on the Aron plan, Fig. 17, are
used, a card being supplied on which the readings are entered exactly
similar to the method adopted with gas. The service mains terminate at
the meter, where the company fix for their own purposes a double pole
switch of the author’s design, Fig. 26, which enables both wires to
be disconnected, a spring shut-off, marked S S, prevents the
switch being left partly on.


SYSTEM OF DISTRIBUTION.

The mains from the Kensington Court Station are laid underground in
a culvert 18 in. by 12 in., which is built with brickwork and cement
under the pavement. A double conductor of flat copper, 0·25 square
inches section, is stretched from shackle insulators attached to iron
bars, which are firmly built into the culvert; the continuity of the
circuit is provided by means of stranded wire, which connects each
section; the flat copper rests on the top of porcelain insulators,
fixed on vertical iron pieces, which are built into the floor.
Connections with the sewers are left for drainage, and six surface
boxes are provided for every hundred yards. Where house connections
have to be made, the branch wires are united by soldering to the bare
copper mains. For crossing under the streets a heavily insulated cable
is employed, and is led through cast-iron pipes.

[Illustration: FIG. 26.]

Until a larger amount of mileage is actually at work, it is difficult
to express an opinion as to which is the cheapest and most efficient
method of laying conductors in the streets. The relative cost of two
plans tried at Kensington Court—the insulated and the bare cable in a
culvert—was given by Mr. Crompton in the following Tables, No. 1 and
No. 2, which are taken from a paper read before the Society of
Telegraph Engineers and Electricians on April 12th, 1888.

Table No. 1 refers more particularly to what is known as the
Callender-Webber system of using bitumen concrete, which is compressed
into blocks or cases usually about 6 ft. long, 8 in. by 5½ in. section,
having two-inch holes through which the insulated copper cable is led.

The estimates given in Table No. 2 were criticised by Mr. Kapp, who
thought that “a more reliable conductor could be obtained by using a
high-class lead-covered cable, which might be laid in the ground with
the simple protection of a rough tarred plank to cover it.” The cost of
digging the trench and running in the cable from the drum was quoted at
3_s._ a yard, and the total cost, inclusive of £10 for surface boxes,
at £155 per 100 yards, instead of £187, as shown by the Table.


TABLE I.

_Cost of Laying 100 Yards of Double Conductor underneath the Footway
of a London Street._

    -------------------------------+---------+--------+--------+
                                   | Single. |  7/16  | 19/15  |
                                   | No. 16. |        |        |
    -------------------------------+---------+--------+--------+
    Area, square inch              |  ·0032  | ·0225  |  ·0773 |
    Area, square millimetre        |  2·08   |  14·6  |    50  |
    Weight per 100 yards run   lb. |   7½    |  53½   |   183¼ |
    Cost of copper at 7¾_d._       |£ 0  4 10| 1 14  6| 5 18  0|
    Cost of insulation             |  1  3  2| 4  8  6|11  2  0|
                                   +---------+--------+--------+
          Total cost of Cables     |  1  8  0| 6  3  0|17  0  0|
    Casing, bitumen, and cement    |  5  3  0| 5  5  0| 8  0  0|
    Labour, Laying                 |  3  0  0| 4  0  0| 5  0  0|
    Trenching and repairing        | 25  0  0|25  0  0|25  0  0|
    Surface boxes and connection   |  5  0  0| 7  0  0|10  0  0|
    Engineer and superintendent    |  3  0  0| 4  0  0| 5  0  0|
                                   +---------+--------+--------+
          Total                    |£42 11  0|51  8  0|70  0  0|
    Add extra if copper, at        |         |        |        |
      9½_d._                       |  0  1  1| 0  8  0| 1  7  0|
                                   +---------+--------+--------+
                                   | 42 12  1|51 16  0|71  7  0|
    Cost of copper per lb.,        |         |        |        |
      laid complete                |  5 13  6| 0 19  4| 0  7  9|
    Current in ampères             |   1·2   |  8·1   |   28   |
    Cost per ampère                | 35 10  0| 6  8  0| 2 10  6|
    -------------------------------+---------+--------+--------+

    -------------------------------+--------+---------+
                                   | 19/12  |  19/10  |
                                   |        |         |
    -------------------------------+--------+---------+
    Area, square inches            | ·1613  |   0·25  |
    Area, square millimetres       |   104  | 161·25  |
    Weight per 100 yards run   lb. |   392  |   576   |
    Cost of copper at 7¾_d._       |12 13  0| 18 15  0|
    Cost of insulation             |24 17  0| 35 17  0|
                                   +--------+---------+
          Total cost of Cables     |37 10  0| 54 12  0|
    Casing, bitumen, and cement    |12 10  0| 12 10  0|
    Labour, Laying                 | 5  0  0|  6  0  0|
    Trenching and repairing        |25  0  0| 25  0  0|
    Surface boxes and connection   |10  0  0| 10  0  0|
    Engineer and superintendent    | 5  0  0|  6  0  0|
                                   +--------+---------+
          Total                    |95  0  0|114  2  0|
    Add extra if copper, at        |        |         |
      9½_d._                       | 2 17  0|  3  5  0|
                                   +--------+---------+
                                   |97 17  0|117  7  0|
    Cost of copper per lb.,        |        |         |
      laid complete                | 0  5  0|  0  4  1|
    Current in ampères             |    58  |    90   |
    Cost per ampère                | 1 13 9 | 1   6  0|
    -------------------------------+--------+---------+

    -------------------------------+-------------+-------------+
                                   |   37/10     |  Two Sets.  |
                                   |             |    37/10    |
    -------------------------------+-------------+-------------+
    Area, square inches            |    0·5      |    1·0      |
    Area, square millimetres       |    322      |    645      |
    Weight per 100 yards run   lb. |    1153     |    2306     |
    Cost of copper at 7¾_d._       |  37  5  0   |  74 10  0   |
    Cost of insulation             |  70 15  0   | 141 10  0   |
                                   +-------------+-------------+
          Total cost of Cables     | 108  0  0   | 216  0  0   |
    Casing, bitumen, and cement    |  16  0  0   |  22  0  0   |
    Labour, Laying                 |  10  0  0   |  18  0  0   |
    Trenching and repairing        |  25  0  0   |  25  0  0   |
    Surface boxes and connection   |  10  0  0   |  10  0  0   |
    Engineer and superintendent    | 10  0  0    |  10  0  0   |
                                   +-------------+-------------+
          Total                    | 179  0  0   | 301  0  0   |
    Add extra if copper, at        |             |             |
      9½_d._                       |   8 10  0   |  17  0  0   |
                                   +-------------+-------------+
                                   | 187 10  0   | 318  0  0   |
    Cost of copper per lb.,        |             |             |
      laid complete                |   0  3  3½  |   0  2  8¾  |
    Current in ampères             |     180     |    360      |
    Cost per ampère                |   1  1  0   |   0 17  6   |
    -------------------------------+-------------+-------------+

    -------------------------------+-------------+-------------+
                                   |  Four Sets. |  Six Sets.  |
                                   |    37/10    |   37/10     |
    -------------------------------+-------------+-------------+
    Area, square inches            |     2·0     |     3·0     |
    Area, square millimetres       |    1290     |    1935     |
    Weight per 100 yards run   lb. |    4612     |    6918     |
    Cost of copper at 7¾_d._       | 149  0  0   | 224  0  0   |
    Cost of insulation             | 283  0  0   | 424  0  0   |
                                   +-------------+-------------+
          Total cost of Cables     | 432  0  0   | 648  0  0   |
    Casing, bitumen, and cement    |  40  0  0   |  55  0  0   |
    Labour, Laying                 |  35  0  0   |  50  0  0   |
    Trenching and repairing        |  30  0  0   |  35  0  0   |
    Surface boxes and connection   |  10  0  0   |  10  0  0   |
    Engineer and superintendent    |  20  0  0   |  25  0  0   |
                                   +-------------+-------------+
          Total                    | 567  0  0   | 823  0  0   |
    Add extra if copper, at        |             |             |
      9½_d._                       |  34  0  0   |  51  0  0   |
                                   +-------------+-------------+
                                   | 601  0  0   | 874  0  0   |
    Cost of copper per lb.,        |             |             |
      laid complete                |  0  2  7¼   |  0  2  6¼   |
    Current in ampères             |    720      |   1,080     |
    Cost per ampère                |  0  16  8   |  0 16 1     |
    -------------------------------+-------------+-------------+


TABLE II.

_Cost of Laying 100 Yards of Double Conductor of Bare Copper carried
on Insulators in a Culvert._

    ---------------------------+----------+---------+---------+
    Area in square inches      |   0·25   |  0·5    |   1·0   |
    Area in square millimetres |  161·25  | 322·5   |   645   |
    Weight of copper in lb.    |          |         |         |
       per 100 yards           |   576    |  1153   |  2306   |
    Cost of copper at          |          |         |         |
       7¾_d._ per lb.          | £18 15  0| 37  5  0| 74 10  0|
    Laying                     |   9  0  0|  9 12  0|  9 12  0|
    Insulators                 |   0  4  6|  0  4  6|  0  4  6|
    6 surface boxes and        |          |         |         |
      connections              |  10  0  0| 10  0  0| 10  0  0|
    Culvert, 18 inches ×       |          |         |         |
       12 inches, for          |          |         |         |
       two lines conductor,    |          |         |         |
       in brickwork            |  53  8  0| 53  8  0| 53  8  0|
       and cement, replacing   |          |         |         |
       pavement                |          |         |         |
    Engineers and              |          |         |         |
       superintendence         |   6  0  0| 10  0  0| 10  0  0|
                               +----------+---------+---------+
          Total                | £97  7  6|120  9  6|157 14  6|
    Extra for copper at        |          |         |         |
       9½_d._ per lb.          |   3  5  0|  8 10  0| 17  0  0|
                               +----------+---------+---------+
          Total                |£100 12  6|128 19  6|174 14  6|
    Cost of copper per lb.     |          |         |         |
        laid complete          |  42_d._  | 27_d._  | 18·2_d._|
    Current in ampères         |    90    |  180    |  360    |
    Cost per ampère            |   1  2  3|  0 14  5|  0  9  8|
    ---------------------------+----------+---------+---------+

    ---------------------------+---------+---------+-------------
    Area in square inches      |   2·0   |  2·55   |  3·00
    Area in square millimetres |  1290   |  1645   |  1935
    Weight of copper in lb.    |         |         |
      per 100 yards            |  4612   |  6125   |  6918
    Cost of copper at          |         |         |
      7¾_d._ per lb.           |149  0  0|190  0  0|224  0  0
    Laying                     |  9 15  0|  9 15  0| 10  0  0
    Insulators                 |  0  4  6|  0  4  6|  0  4  6
    6 surface boxes and        |         |         |
      connections              | 10  0  0| 10  0  0| 10  0  0
    Culvert, 18 inches ×       |         |         |
      12 inches, for           |         |         |
      two lines conductor,     |         |         |
      in brickwork             | 53  8  0| 53  8  0| 53  8  0
      and cement,              |         |         |
      replacing pavement       |         |         |
    Engineers and              |         |         |
      superintendence          | 10  0  0| 10  0  0| 15  0  0
                               +---------+---------+-------------
          Total                |232  7  6|263  7  6|312 12  6
    Extra for copper at        |         |         |
      9½_d._ per lb.           | 34  0  0| 43 10  0| 51  0  0
                               +---------+---------+-------------
          Total                |266  7  6|306  7  6|363 12  6
    Cost of copper per lb.     |         |         |
      laid complete            | 13·8_d._|  12_d._ |  12 6_d._
    Current in ampères         |   720   |  910    |  1080
    Cost per ampère            |  0  7  5|  0  6  9|  0  6  8½
    ---------------------------+---------+---------+-------------


THE VIENNA CENTRAL-STATION.

The practical success of the Battery Transformer system has been
demonstrated at Vienna, where an installation of five thousand lamps
in the Opera House and Burg Theatre was maintained for the past year
from a distributing station 1,400 yards away. The boilers are fixed
in a basement formed by excavating the court-yard of a private house
to a depth of 15 feet 6 in. below the street level; the building
itself is utilised partly for offices and partly as a large dynamo and
engine-room. Each dynamo is designed to give an output of 72 kilowatts
or 120 ampères, at 600 volts pressure. The current is led by means of a
lead-covered cable underground to the accumulators, which are erected
in groups of 52 cells each, so as to give 100 volts to the lamps, with
a comfortable margin. The total pressure required to charge the four
groups of batteries in series varies from 430 volts at the time the
batteries are giving off work, to 480 volts for the short time during
which the charge is being completed. During five hours of lighting
about two-thirds of the current comes direct from the dynamos; but
during this time, for short periods, the demand for current often
increases to such an extent that these proportions may be reversed, and
the batteries supply two-thirds of the total.

The regulation of groups of batteries placed in series is not a
difficult matter, and will be understood by referring to the following
diagram, Fig. 27:—

[Illustration: FIG. 27.]

The four battery stations mentioned as arranged in series are
represented. The current may be supposed to enter at the right hand
corner, passing through the first battery with the lamps parallel to
it, and from that battery to the commencement of the next, and so on
through the third and fourth, the current being varied at will at the
central-station, or kept constant by means of an electrical governor.
The potential for each of the four groups of lamps is maintained in
the following manner:—In each group one terminal is kept permanently
connected to one of the discharge mains and to one of the charging
mains; the other terminal can be shifted from cell to cell according to
the E. M. F. required in the corresponding lamp circuit by means of a
contact regulator. This movable terminal is shown by the bunch of lines
at one extremity of each battery group. The rule for charge and
discharge is, that the terminal cell at the regulating end of the
battery is so arranged that it neither receives nor gives off current,
so that there is no loss of energy in the shape of E. M. F. The contact
regulator, which was designed by Mr. Crompton for use at Kensington
Court, is shown by Fig. 28:—

[Illustration: FIG. 28.

CENTRAL-STATION.]

The ring contacts are arranged in a line in such a manner that a
circular contact-piece, made of thin sheets of copper, can be forced
through them in turn by means of a central screw spindle. The mains for
charge and discharge are attached to the fixed disc contacts on the
central screws, and the regulating cells of the battery are coupled to
their respective contact rings by sockets at the back of the board.

The difficulty with the battery transformer system is the introduction
of 400 to 500 volts into the houses, which would be necessary
without the batteries are always fixed in sub-stations from which
a low-pressure current, say of 100 volts E. M. F., could only be
distributed.

A method has been devised by Mr. Henry Edmunds to obviate this
disadvantage. He also uses the high-tension current to charge the
batteries, but by means of a distributor, which is automatically
worked by the current, each group of cells is charged in turn, when it
is entirely cut off from the supply main to the house, through which
current is perhaps being taken for lighting purposes. The system is now
being adopted by the Cadogan Electricity Supply Company, Chelsea.


DIRECT-CURRENT TRANSFORMERS OR DYNAMOTORS.

The method of transforming by direct current without the aid of
batteries is not practically at work; but, as the advantages are so
obvious and its development is only a question of time, a description
of the system may not be considered out of place.

The electrical exhibition at Philadelphia in 1884 contained a dynamotor
which was exhibited by the Van de Poele Electric-Light Company, but,
as far as could be ascertained, was not worked, and, as it was simply
described as an induction machine for distributing currents for the use
of incandescent and other lights, it attracted little attention.

The advantages of an alternating current transformer system of
distribution, Class II., has been put forward in these pages,
especially that of simplicity and cheapness. An alternating current
dynamo for a given output is cheaper than a direct, and it takes less
labour to look after it, because it has no commutator.

An alternating transformer is also an exceedingly simple piece of
apparatus. If originally made with due care and kept in a dry place, it
never breaks down, as it has no moving parts, and so there is nothing
to go wrong.

The alternating system of distribution has, however, some very serious
disadvantages. In the first place, it is most important that motors
should be driven during the day when the lights are not in use. In the
second, batteries cannot be used in an alternating current system, so
any immunity from breakdown that they might ensure is wanting; and
steam must be kept up all day and all night.

If motors are wanted during the day, so that the load on the engine is
nearly constant, batteries are not so valuable, except with a view of
preventing a breakdown; but, if batteries cannot be used, the advantage
of using motors becomes enormous, as the plant has to be large enough
to supply the maximum load, and would otherwise be idle during the day.

In alternating current systems there are two difficulties in the way
of using motors. It is difficult to make an alternating current motor
that will start, and, if that difficulty is surmounted, it is difficult
to make an alternating current motor that will work on varying loads
without great waste of power. The question of the efficiency of
alternating current motors has never been really practically studied
yet; and, until these difficulties are overcome, we must regard
alternating current motors as non-existent. Several methods of working
alternating current transformers off direct currents by commutating the
primary have been proposed at different times; but they all seem to be
impracticable, and it seems impossible to get over the difficulties
that arise from sparking when it is attempted to break a high-tension
circuit.

One of the first methods of distribution over large areas proposed was
by means of motors and dynamos combined. For instance, suppose, in
order to keep down the size of the leads, 2,000 volts are used in the
mains, a motor capable of working with 2,000 volts is put down where
the lights are wanted, and this is made to drive a dynamo giving 100
volts and a large current. Instead of having a separate motor and a
dynamo connected by a belt or by coupling the spindles together, it is
simpler to make one machine with two armatures, or to have only one
armature with two circuits on it. One circuit is wound with fine wire
and takes the 2,000 volts and tends to turn the armature round. The
other circuit is wound with thick wire giving 100 volts and a large
current, and tends to stop the armature, thus absorbing the power
supplied by the high-pressure circuit. The direct-current transformer
or dynamotor is thus a sort of double dynamo, or dynamo and motor
combined. If it gets 2,000 volts and 10 ampères, it would, if there
were no waste, give 100 volts and 200 ampères; with a waste of 10 per
cent., it will give 100 volts and 180 ampères.

In the United States it is usual to place an alternating current motor
in each house to be lighted; but the conditions are quite different
there, overhead wires being used extensively. In this country this
system is not likely to find favour, and local sub-stations will be
used, the high pressure, which is always dangerous to life, will
thus be kept out of private houses and offices. There is, then,
very little difference in the cost of maintenance of alternating
current transformers and dynamotors, and the advantages possessed
by alternating current transformers in this respect are more than
counter-balanced by the use of motors on direct current circuits.

Dynamotors have not come into general use yet because no stations have
been started in this country of the size which demands them. No central
station with sub-stations is in operation, but there is every reason to
expect several will be soon; and it is very necessary to discuss the
various methods, not only in use at this moment but coming into use in
the immediate future. The dynamotor itself needs no working out, as
any maker of direct-current dynamos can, of course, make them. Messrs.
Paris and Scott of Norwich showed some in operation at the Newcastle
Exhibition in 1887; the most successful type is that recently invented
by Mr. Jas. Swinburne, illustrated by Fig. 29. The backward main round
primary or motor magnet is shown on the left, and the forward main
round the secondary or dynamo magnet on the right, the outside coil
round both magnets is the shunt.

[Illustration: FIG. 29.]

The dynamotor may be made with two circuits on one armature as
already explained, or it may have two armatures in separate fields,
still making up one machine. The first arrangement has two grave
disadvantages. There is difficulty about securing perfect insulation
between the two circuits, and this leads to chances of danger in the
houses. A dynamotor with two circuits on one armature cannot be
compounded, that is to say, it cannot be made to give constant
electrical pressure on the mains if the number of lamps is varied. A
Swinburne double armature machine can be compounded, not only to give
constant pressure with a varying load, but to give constant electrical
pressure even if both the load and the pressure on the primary circuit
vary. This makes a considerable difference in the copper of the primary
leads, as in large and complicated districts it is almost impossible
to arrange leads, even when working with high electrical pressure and
small currents, so that the electrical pressure remains constant,
or even nearly so. A very small variation of the pressure on an
incandescent lamp makes an enormous difference in the amount of light
it gives, and in its duration. It is, therefore, most important that
the E. M. F. on the lamps should be kept absolutely constant.

This difficulty is, of course, insurmountable in the case of
alternating current transformers. Alternating current transformers
cannot be made to compound, and the loss in leads cannot be corrected
by them, so that the lamps burn dull at full load.

If secondary batteries are used at the sub-stations, the reduction of
pressure might be effected by them. A number would be charged in series
and discharged in parallel. This arrangement needs at least two sets
of cells, and cells are expensive; and it is difficult to preserve the
insulation of cells with such electrical pressure as 2,000 volts. If
cells are used for the purpose of equalising the load or as a safety
reserve, it is better to charge them by means of a dynamotor.


INSTALLATION AND WORKING COST OF CENTRAL-STATIONS.

Until the balance-sheet of some large central-station has been
published, it is impossible to do more than surmise what relation the
earning power of the generating plant bears to the initial cost. Those
central-stations which are working successfully in this country at the
present time are either too small for a reliable estimate to be formed,
or, as in the case of the Grosvenor Gallery, the space is too cramped
for the large amount of machinery which it has been found necessary
to add in order to meet the increasing demands for light. In order to
obtain an approximate idea of the cost of installing a station capable
of maintaining 10,000 lights, the following data (Table III.) given
in Mr. Crompton’s paper before the Society of Telegraph Engineers are
extremely valuable and will be examined with interest.

Although the figures given are necessarily empirical and open to
criticism, the cost with both systems of distribution is approximately
the same, and may be taken roughly at £5,860 per 1,000 lights, which
amount, according to Professor Forbes, would be reduced to £3,914 per
1,000 lights if the installation was put down according to American
practice, and at the initial cost of the Westinghouse alternating
current system.

Mr. Crompton also compares the working cost of the two systems (Table
IV.).

TABLE III.

_Cost of 10,000-Light, or 600-Kilowatt_,[6] _Plant._

    A.T.—ALTERNATING TRANSFORMER DISTRIBUTION.

    Generating station, buildings, chimney shaft,                £
      water tanks, and general fittings                        11,000
    Dynamos and exciters—865 kilowatts, including
      spare sets, divided as convenient                         5,540
    Motive power, _i.e._, engines, boilers, steam
      and feed connections, belts, &c., at £8 12_s._
      per I.H.P.                                               12,470
    500 transformers, _i.e._, one to every pair of
      houses, at £15 each                                       7,500
    2,000 yards primary or charging main, exterior
      to area of supply, at £308 per 100 yards                  6,160
    20,000 yards distributing main, 50 mm. sectional
      area, at £91 7_s._ (_see_ Table I.)                      14,270
    Regulating gear                                               500
                                                              ———————
                                                              £57,440
                                                              =======

    B.T.—ACCUMULATOR TRANSFORMER DISTRIBUTION.

    Generating station, buildings, chimney stack,                £
      water tanks, and general fittings                         8,000
    Dynamos—600 kilowatts, in six sets of 100
      kilowatts each                                            4,800
    Motive power, _i.e._, engines, boilers, steam
      and feed connections, &c., at £8 12_s._
      per I.H.P.                                                8,600
    4 groups of accumulators, in all 240 cells, in
      series, at £40 per cell, including stands                 9,600
    2,000 yards charging main, at £306 17_s._ 6_d._
      per 100 yards (_see_ Table II.)                           6,137
    20,000 yards distributing main, 161·25 mm. sectional
      area, at £100 12_s._ 6_d._ (_see_ Table II.)             20,125
    Regulating gear                                             2,500
                                                              ———————
                                                              £59,762
                                                              =======

[6] Kilowatt equals 1,000 watts.


TABLE IV.

         _Working Expenses and Maintenance of 10,000-Light,
                        or 600-Kilowatt, Plant._

    -------------------------------+-----------------------------------+
                                   |        Direct Alternating         |
                                   |        Transformer System.        |
    -------------------------------+-----------------+-----------------+
    _Materials_—                   |   £   _s._ _d._ |   £   _s._ _d._ |
     Coals: 4,380 tons at 17_s._   | 3,723  0    0   |                 |
       ”    2,550   ”     17_s._   |       · ·       |                 |
     Oil, water, and petty stores: |                 |                 |
        1,500 hours at 7_s._ 6_d._ |                 |                 |
        7,250 hours at 1_s._       |   925  0    0   |                 |
        1,400 hours at 5_s._       |       · ·       |                 |
          Total cost of material   +-----------------+ 4,648  0    0   |
                                   |                 |                 |
    _Labour_—                      |                 |                 |
      2 foreman drivers at 45_s._; |                 |                 |
      6 drivers at 30_s._;         |                 |                 |
      9 firemen at 24_s._;         |                 |                 |
         sundry labour             | 1,388  8     0  |                 |
                                   |                 |                 |
      1 foreman driver at 45_s._;  |                 |                 |
      2 drivers at 30_s._;         |                 |                 |
      3 firemen at 24_s._;         |                 |                 |
         sundry labour             |                 |                 |
                                   |                 |                 |
    _Salaries_—                    |                 |                 |
       1 chief at £500;            |                 |                 |
       2 assistants at £200 each;  |                 |                 |
       4 clerks at £80 each        | 1,220  0     0  |                 |
                                   |                 |                 |
       1 chief at £500;            |                 |                 |
       1 assistant at £200;        |                 |                 |
       4 clerks at £80 each        |       · ·       |                 |
                                   +-----------------+ 2,608  8    0   |
    _Maintenance of Plant_—        |                 |                 |
      Motive power and dynamos:    |                 |                 |
        10 per cent. on £18,010    | 1,801  0     0  |                 |
        10 per cent. on £13,400    |       · ·       |                 |
      Buildings and fittings:      |                 |                 |
         5 per cent. on £11,000    |   550  0     0  |                 |
         5 per cent. on £8,000     |       · ·       |                 |
      Transformers:                |                 |                 |
        10 per cent. on £7,500     |   750  0     0  |                 |
      Accumulators:                |                 |                 |
        15 per cent. on £9,600     |       · ·       |                 |
      Mains:                       |                 |                 |
         7½ per cent. on £20,430   | 1,532  5     0  |                 |
         2½ per cent. on £26,262   |       · ·       |                 |
      Regulating gear:             |                 |                 |
        10 per cent. on £500       |    50  0     0  |                 |
        10 per cent. on £2,500     |       · ·       |                 |
                                   +-----------------+ 4,683  5    0   |
                                   |                 +-----------------+
                                   |                 |11,939 13    0   |
                                   |                 +-----------------+
      2,100 units × 365 days       |                 |                 |
            = 766,500 units.       |                 |                 |
               Cost per unit       |       · ·       |    3·75_d._     |
    ====================================================================
                                   |         Continuous Battery        |
                                   |         Transformer System.       |
    -------------------------------+-----------------+-----------------+
    _Materials_—                   |   £   _s._ _d._ |   £   _s._ _d._ |
     Coals: 4,380 tons at 17_s._   |       · ·       |                 |
       ”    2,550   ”     17_s._   | 2,167  0    0   |                 |
     Oil, water, and petty stores: |                 |                 |
        1,500 hours at 7_s._ 6_d._ |                 |                 |
        7,250 hours at 1_s._       |       · ·       |                 |
        1,400 hours at 5_s._       |   350  0    0   |                 |
          Total cost of material   +-----------------+ 2,517  0    0   |
                                   |                 |                 |
    _Labour_—                      |                 |                 |
      2 foreman drivers at 45_s._; |                 |                 |
      6 drivers at 30_s._;         |                 |                 |
      9 firemen at 24_s._;         |                 |                 |
         sundry labour             |                 |                 |
                                   |                 |                 |
      1 foreman driver at 45_s._;  |                 |                 |
      2 drivers at 30_s._;         |                 |                 |
      3 firemen at 24_s._;         |                 |                 |
         sundry labour             |  975  0    0    |                 |
                                   |                 |                 |
    _Salaries_—                    |                 |                 |
       1 chief at £500;            |                 |                 |
       2 assistants at £200 each;  |                 |                 |
       4 clerks at £80 each        |       · ·       |                 |
                                   |                 |                 |
       1 chief at £500;            |                 |                 |
       1 assistant at £200;        |                 |                 |
       4 clerks at £80 each        | 1,020  0    0   |                 |
                                   +-----------------+ 1,995  0    0   |
    _Maintenance of Plant_—        |                 |                 |
      Motive power and dynamos:    |                 |                 |
        10 per cent. on £18,010    |       · ·       |                 |
        10 per cent. on £13,400    | 1,340  0    0   |                 |
      Buildings and fittings:      |                 |                 |
         5 per cent. on £11,000    |       · ·       |                 |
         5 per cent. on £8,000     |   400  0    0   |                 |
      Transformers:                |                 |                 |
        10 per cent. on £7,500     |       · ·       |                 |
      Accumulators:                |                 |                 |
        15 per cent. on £9,600     | 1,440  0    0   |                 |
      Mains:                       |                 |                 |
         7½ per cent. on £20,430   |       · ·       |                 |
         2½ per cent. on £26,262   |   656 10    0   |                 |
      Regulating gear:             |                 |                 |
        10 per cent. on £500       |       · ·       |                 |
        10 per cent. on £2,500     |   250  0    0   |                 |
                                   +-----------------+ 4,086 10    0   |
                                   +                 +-----------------+
                                   |                 | 8,598 10    0   |
                                   +                 +-----------------+
      2,100 units × 365 days       |                 |                 |
            = 766,500 units.       |                 |                 |
               Cost per unit       |       · ·       |     2·7_d._     |
    -------------------------------+-----------------+-----------------+

With the exception of the amount allowed for depreciation of the
accumulators, which time alone can show to be correct, the expenses
may be said to be over rather than under-estimated; the 15 per cent.
depreciation given in Table IV. is under what has hitherto been found
necessary to allow for the renewal of the plates of a secondary battery.

If the mean of the two results in Table IV. are taken, the working cost
per Board of Trade Unit will be 3·22_d._, which shows that with both
systems, after making due allowance for interest on capital, directors’
fees, bad debts, and other sundries omitted by Mr. Crompton, there is a
probability of a very fair return on the capital expenditure, and the
prospect of a handsome dividend for an electric lighting company who
can sell electricity at the average price of 7_d._ per Unit.

       *       *       *       *       *

The cost of maintaining and working electric lighting plant at
private installations is usually much in excess of a supply from a
central-station; but where the installation is over 500 lights, the
difference is not very great.

The working cost at the Athenæum Club of 387 lamps for the past year is
given as follows:—

                                 £    _s.   d._
    Gas for gas-engine          446    7    10
    Oil     ”     ”              71    3     8
    Water   ”     ”              35    0     0
    Wages                       175    2     1
    Sundries                     30    3     0
    Maintenance of lamps, etc.   98    4     1
    Repairs                     103    1     1
                               —————
                               £959    1     9
                               —————

Average cost of lighting by gas and oil for previous years, for
two-thirds number of lights £840.

At the Naval and Military Club, 420 lights cost £821 18_s._ for the
same period, a steam-engine being used instead of a gas-engine.

The annual report of the cost of the electric light at the South
Kensington Museum shows that in a larger installation, consisting both
of arc and incandescent lamps, the annual cost of the latter is much
less than in either of the clubs mentioned. At the Museum there are 860
16 candle-power lamps, working 655½ hours per annum, or 562,387 lamp
hours; the total cost for working last year was £386, which includes
£66 for repairs of engines, boilers, dynamos, and maintenance of lamps;
but rent, interest on capital, depreciation of plant, and management
is not included. The light is used only three evenings a week, so that
the wages of the attendants are proportionately in excess of what they
would be in a central-station.

       *       *       *       *       *

The cost of arc lighting for street purposes may be estimated from the
following tenders. At Taunton the local electric light company offered
to extend the lighting of streets from 29 to 60 arc lamps of 1,200
candle-power nominal on the Thomson-Houston system, at the following
rate:—

                                                       Per annum.
                                                        £ _s.   d._
    Burning on average of 6 hours per night each lamp  17   7   6
                          7       ”            ”       18  12   6
                          8       ”            ”       19  17   6

The posts and supports to be provided and fixed by the company, or, if
the town council found the same, the company would allow a deduction at
the rate of 5 per cent. per annum upon the outlay made by the council.
The lamps are usually about 400 feet apart.

The actual cost of operating arc lights on this system is given in the
following detailed expenses of a six hours’ run of a 50-light plant for
the street lighting of an American city:—

    2,600 lb. Ind. nut and slack coal, at $1·30 per ton     $1·69
    Engineer, one night, at $50·00 per month                 1·67
    Superintendent or electrician, one night, at $50·00
       per month                                             1·67
    Trimmer, one day, at $40·00 per month                    1·33
    48 pairs of carbons, at $18·50 per month                   89
    Waste, &c., at $20·00 per year                             05
    Water rent, at $40·00 per year                             11
    Half-pint cylinder oil, at 60c. per gallon                 04
    One pint engine and dynamo oil, at 50c. per gallon         06
    One day repairs on machine and lamps, including
       globes, at $120·00 per year                             33
    One day taxes on 50-light plant, assessed at $5,000,
       at 2¼ per cent.                                         31
    One day interest on 50-light plant ($10,000), at 6 per
       cent.                                                 1·67
                                                            —————
     Making a total of                                      $9·82
      10½_d._ or 20·45 cents. per lamp. £15 10_s._ per annum.

If, in addition to the 50 street lights, 33 other arc lights are
maintained, the total cost is reduced for a six hours’ run to $13·25,
or £2 15_s._ 2_d._ for the 83 lights, 8_d._ or 15·96 cents per lamp,
£12 3_s._ 4_d._ per annum.

Table V. has been calculated by M. Decker, of Nuremburg, and gives
the comparative cost of working 150 lamps by electricity and by gas.
The gas price (1) is that paid in Paris, namely, 6_s._ 9_d._ per 1000
cubic feet; column (2) is the price usually taken commercially, which
includes the fixed charges. The price of electricity is given: 1st,
when a steam-engine is available; 2nd, when it is necessary to lay down
a special engine; 3rd, when a gas-engine is used the gas is charged at
a trifle over the price in column (1).

TABLE V.

_Total Cost per Hour and per Lamp._

         Legend for Table V.
    A = Number of hours’ work per year.
    B = Number of hours’ work per day.
    C = Steam-engine (existing).
    D = Hydraulic Motor.
    E = Steam-engine to be erected.
    F = Gas engine
    G = (1) Gas at 6_s._ 9_d._ per 1,000 ft.
    H = (2) Gas at 8_s._ 9_d._ per 1,000 ft.

   --------+------+--------+--------+---------+---------+-------+------
           |      |        |        |         |         |       |
        A  |  B   |   C    |   D    |   E     |    F    |   G   |   H
           |      |        |        |         |         |       |
   --------+------+--------+--------+---------+---------+-------+------
           |      | Pence. | Pence. |  Pence. |  Pence. | Pence.| Pence.
      500  | 1·38 | 0·485  |        |  1·055  |  1·216  | 0·418 | 0·552
      800  | 2·19 | 0·371  |        |  0·780  |  1·007  | 0·399 | 0·513
    1,200  | 3·29 | 0·314  |        |  0·608  |  0·865  | 0·380 | 0·352
    3,600  | 9·87 | 0·219  | 0·152  |  0·352  |  0·485  | 0·361 | 0·465

         Arc Lamps.
      500  | 1·38 | 5·235  | 4·246  | 10·459  | 11·485  |       |
      800  | 2·19 | 3·971  | 3·089  |  7·552  |  9·272  |       |
    1,200  | 3·29 | 3·087  | 2·441  |  6·004  |  7·581  |       |
    3,600  | 9·87 | 2·185  | 1·510  |  3·591  |  5·586  |       |
   --------+------+--------+--------+---------+---------+-------+------


UNDERGROUND OR OVERHEAD WIRES.

Apart from the unsightly appearance of overhead wires, there are many
reasons why any extended system of supply of electricity should be
carried out by underground cables. It is true that there have been no
accidents in this country due to electric light wires falling, owing to
the care bestowed on their insulation and erection; on account of the
heat generated by the passage of the current through the leads no snow
can accumulate on them, and therefore they are not subjected to the
extra weight which destroyed so many of the telegraph and telephone
wires in the last snow storm. Overhead electric light wires are
exclusively used by the largest electric-supply company in London, and
it is probable that, without further legislation takes place, other
companies will shirk the expense of an underground system; and even
a more dangerous method of running cables than that which has been
condemned in the principal cities of the United States will become
not the exception but the rule. In the city of New York the process
of conversion of the present overhead to an underground system is a
fact about to be accomplished to a very great extent at least, in the
near future. Since July, 1887, the Western Union Telegraph Company
have occupied the conduits, which have been constructed and laid with
some 500 miles of wire; also the Metropolitan Telephone and Telegraph
Company have 1000 miles of wire in the subways; and the Edison
Illuminating Company, whose conductors were laid in the trench at the
time of construction, has more than 1000 miles of underground cable.
The plan adopted is to build conduits of section, as in Fig. 30, which
shows the subway in course of construction, with man-hole opening and
exposed ends of conduits. The single tube at top is for distribution
between man-holes, and some wires are shown entering the vault on the
right from the service box in the foreground. The conduits are of
various types; creosoted wooden tubes are placed in creosoted wooden
casings; wrought-iron pipes are sometimes laid in asphaltic concrete
with creosoted wooden box; another arrangement is to be of composition
blocks on concrete, and cover them with brick—or wrought-iron pipe
is lined with cement, and laid in hydraulic cement concrete and cased
with creosoted plank. About 85 per cent. of all the conduits have been
constructed on this plan, the interior diameter of the pipes being 2½
inches.

[Illustration: FIG. 30.]

[Illustration: FIG. 31.]

Fig. 31 shows how the street arc lighting wires are taken, also a
branch for house use, out of the man-holes, which are placed at each
street crossing. For the cleaning purposes and for drawing the cable
through the conduits, these must be laid practically straight.

[Illustration: FIG. 32.]

Fig. 32 illustrates a method proposed by Mr. Kenneth Mackenzie, which
is somewhat similar to the system of conduit which, used at Tours
for the past two years, has been found most efficient for the high
potential supply mains to the transformers. The troughs would be about
4 ft. long and 15 in. deep, having spigot and socket joints at the ends
like ordinary water pipes. Transverse pieces of wood, or preferably
slate, would rest upon projections, and would support the mains, and
a cover recessed as shown would make the conduit fairly water-tight;
drain holes would be provided, and the branches to houses led off
through glands in the side of troughs. The American plan is, doubtless,
the best, as there is no space for moisture to collect in the conduits;
but Mr. Mackenzie’s system is well worth trying, and has the advantage
of being much cheaper in first cost.

The Edison plan is to place two solid conductors in a tube which is
filled up solid with an insulating material, suitable bends and offsets
being supplied, so that the tube containing the two conductors can be
buried in the ground like a gas-pipe. The system is very largely used
both in the United States and in Continental cities; but it is doubtful
whether the protection would suffice in our towns, where the streets
are already at the mercy of the gas and water companies, whose workmen,
with a single blow of a pick, might perforate the tube, and cause a
dangerous short circuit.


THE INTERESTS OF GAS COMPANIES AS TO ELECTRIC LIGHTING.

The policy of gas companies with regard to electric light has, with
few exceptions, been a state of indifference to the progress of
things electric, with contempt for a rival whose opposition is not
sufficiently powerful to be appreciated. The chairman of a well-known
gas company stated, what is undisputed,—that the introduction of
electric arc lights was accompanied by an increased consumption of gas
in the immediate neighbourhood where these lights are used; but it is
very doubtful whether this will be the case when incandescent lights
are generally supplied. The introduction of these lights into any
business district would mean the displacement of at least as many
burners as there are electric lamps; and this reduction not only
means loss of income, but also loss by interest on plant which is not
kept at work to the capacity for which it was designed. The question
suggests itself, “Are existing gas companies more favourably situated
for furnishing electricity than any one else?” There are many reasons
in favour of the supposition that the directors of gas companies have
at the present time an opportunity of acquiring almost as complete a
monopoly of lighting by electricity as they have with gas. As regards
central-stations, everything is in their favour; there is generally
some spare ground for the machinery, waste heat could be utilised, and
a cheap fuel in the shape of coke is ready to hand. They have greater
facilities for breaking up streets without danger of troubles arising
with the local authorities, and if the Gasworks Clauses Acts, which
authorise their existence, tie them down to one illuminant, a very
little expenditure would enable them to enlarge their powers. In many
towns the shareholders are local men who wish to use the electric
light, but cannot favour its introduction because they think it would
tend to smaller dividends or lower quotations for their shares; if,
however, a scheme was promoted either by the gas company, or, if that
was impossible, if the directors interested themselves in a separate
electric light undertaking, the security which the gas and water
investments command would, no doubt, cause a sufficient number of local
subscribers to come forward and make even a small installation a paying
concern. The Imperial Continental Gas Association have already taken
up the supply of electricity in Vienna, and are likely to extend this
new branch of their business to the other cities in which they hold
gas concessions; also in the United States the growing opposition of
the electric light companies is being seriously discussed, and already
several gas companies are installing electric light plants.

It is not at all probable that the scare which caused such a drop
in the value of gas shares when the electric light first appeared
will be repeated, but the present high price of gas shares cannot
be maintained. Kerosene lamps have been for some time a far greater
rival to gas than electricity. The cheapening of petroleum, which is
now shipped in bulk to this country in tank steamers, will cause the
consumption to increase, and enable the oil to be supplied at a price
so that it can be used in petroleum-engines, and give a motive power
which will be found to be far more economical than the gas-engine.
The latest development of petroleum-engines is that shown by Messrs.
Priestman at the Royal Agricultural Society’s Show at Nottingham. The
engine in external appearance is like the Otto gas-engine, but uses the
ordinary “paraffin oil” of commerce, which has a high flashing point.
The oil is simply put into a closed tank, and on the top of this, air
is forced which drives the petroleum into a chamber heated by the
exhaust from the engine, where it is partially vaporised and led into
the cylinder with sufficient air to cause it to ignite by means of an
electric spark.

The report of the trials with a 5 horse-power engine show that a brake
horse-power was obtained for 1·7 lb. of oil, or at 6½_d._ per gallon
for 1·4_d._ per horse-power per hour; with the Spiel engine the cost is
stated to be 0·8_d._ per horse-power per hour.

Any serious reverse to the gas industry would cause a great pecuniary
loss to a large number of investors. The paid-up and borrowed capital
devoted to the manufacture and supply of gas in the United Kingdom
exceeds £56,000,000, of which above £36,000,000 appertain to the
companies and the remainder to the local authorities, whose receipts in
respect of their gas undertakings last year exceeded £4,400,000.

The corporation of Bradford, who are owners of the gasworks, have
wisely foreseen that it is better to keep the electric light in their
own hands, and are now about to erect a central-station, and will
lay underground wires; the amount sanctioned for this preliminary
installation is £20,000.


THE LUCIGEN LIGHT.

A few remarks on this method of obtaining light from the combustion
of crude petroleum may be added, as the light has been put forward
as a cheaper and better substitute for the electric arc. The Lucigen
light is produced by burning creosote oil, tar oil, or other heavy
hydro-carbons, by means of compressed air in a special form of lamp,
and consists of a cylinder at the side of which a steam donkey
compressing pump is mounted, or in a more recent form known as the
Wells’ light, no separate air compressor is used, but, instead, the
pressure is obtained from the water mains or from a small force pump.
The cost is stated to be 3_d._ per hour for 2,500 candle-power,
requiring three gallons of oil per hour, but is in reality at the
present time double this owing to the price of the oil, which, under
the most advantageous circumstances, costs on average 2_d._ per
gallon. At the Forth Bridge these lights have been found of use in
illuminating open spaces, but have not supplanted the electric arc
lights which are universally employed for the lighting of the works and
the interior of the shops. The disadvantages are the noise, the oil
shower which pervades the vicinity of the light causing timber staging
to be highly inflammable, and the difficulty of preventing water from
entering the burner, a few drops sufficing to extinguish the light.
The use of the Lucigen light is, therefore, very limited, and it is
probable that, in situations where shadows from the arc light are found
to be objectionable, large incandescent electric lamps, which are
supplied up to 1,500 candle-power, would meet the case; or, failing
these, petroleum could be burnt in lamps similar to those used in
lighthouses with greater safety, and at not much increased cost, than
the compressed-air system.


USEFUL NOTES.

To ascertain in what direction the electric current is flowing through
any wire by means of a pocket compass:—

A current flowing from _south_ to _north_ will always deflect the
needle to the west, providing the wire in which the current flows is
_over_ the instrument.

The word S. N. O. W. expresses this—south north over west; and should
be remembered.

_Another simple plan_ is to hold the outstretched right hand over the
compass; then, if the current flows in the direction of the wrist to
the fingers, the needle will move towards the thumb.

To find the direction of the current in the wire of an electro-magnet:

Place the palm of the hand on the coil with the fingers parallel to
the wires: the thumb will point to the _North Pole_ if the current is
flowing as in previous rule towards the fingers. Conversely: if the
_North Pole_ is known, the fingers will point to the direction of the
current when placed parallel with the wires, with the thumb pointing to
the North Pole.

If no compass is available, take two pieces of lead and place a few
inches apart in a pot containing dilute sulphuric acid, scrape the lead
clean, and join a piece of wire to each and connect to poles to be
tested. After current has passed a short time one piece of lead will
become brown, the other grey; trace the former to the dynamo cable, and
this is the positive, and should be marked with a + or be painted red
for future distinction.


_Incandescent Lights or Glow Lights._

The number of lights required to illuminate any room would vary very
much, according to the style of decoration and position of the lamps.
As a rule, a similar number of glow lamps are required as there would
be gas burners. The former give a much higher standard of illumination,
which, curiously enough, is generally expected with electric lighting
on account of the purity of the atmosphere when the full light is being
used, which is not the case with gas.

One 16 candle-power lamp will light an area of about 8 feet in diameter
at 8 feet above ground; in ordinary situations allow, one lamp for 38
square feet.

_Arc Lighting of Works._

External.—56. 2,000 CP. arc lights will illuminate 160,000 square
yards, or one for each 2,800 square yards.

Internal.—43. 2,000 CP. arc lights will illuminate 31,500 square
yards, or one for each 730 square yards.

_Approximate Cost of Electric Light, Museum._

    Arc lighting, 2/5 gas; with interest, ⅔.
    Incandescent,   ⅔ gas; with interest, 4/3.

_Motive Power._

Compound engine 2 lbs. of coal per indicated horse-power per hour.

Good single-acting engine 3 to 6 per indicated horse-power per hour.

An indicated horse-power can be obtained in a compound engine from 20
lbs. of steam per hour.

A good boiler evaporates 9 to 10 lbs. of water per lb. of coal.

From 21 to 28 cubic feet of gas are required in a gas-engine per
indicated horse-power per hour.

_Incandescent Lamps._

In practice allow 9-60 watt 16 CP. lamps per indicated horse-power of
engine.

_Mem. for Wire Running._

Leads to the left or “low,” “_light coloured_.”

Returns to the right or “raised,” “_red_.”


_English and French Measures._

    Millimetre   =  0·039 inches   1 mill =  ·0254  millimetres.
    Centimetre   =  0·393   ”      1 inch = 2·5399  centimetres.
    Decimetre    =  3·93    ”      1 foot = 3·3480  decimetres.
    Metre        = 39·37    ”      1 yard =  ·91439 metres.
    Cubic metre  = 35·32 cubic feet or 1·31 cubic yards.


ELECTRICAL MEASUREMENTS.

The Paris Congress Units (1884) are now universally adopted and consist
as follows:

_Electro-motive Force, and Potential_ (E).—The Volt. _The legal volt
is ·926 of the E. M. F. of a Daniell’s cell, which for rough purposes
may be taken as a volt._

_Resistance_ (R).—The Ohm. The legal ohm is now represented by the
resistance of a column of mercury of a square millimetre in section at
the temperature of zero centigrade 1·062 metres long.

_Current_ (C).—The Ampère. This is the strength of current sent
through a wire having the resistance of 1 ohm at the E. M. F. of 1 volt.

_Quantity_ (Q).—The Coulomb. It is the quantity of electricity given
by an ampère in a second. One coulomb decomposes ·00142 grain of water.

_Heat or Work_ (W).—The Joule, or Volt-Coulomb, is the work done by 1
coulomb in 1 ohm. The work done by any current per second is obtained
in ergs by the product of the current into the electro-motive force
producing it or W = CE or W = C²R. The Erg is the C. G. S. unit of
work.

_Power_ (P).—The Watt, 1 ÷ 746 of a horse-power, employed in doing 1
joule of work in 1 second.

HP, or the Horse-power, is found by dividing C E by 746, thus (CE)/746
or (C²R)/746 = HP.

See also explanation of terms.


ELECTRICAL TABLE OF THE BIRMINGHAM WIRE GAUGE FOR PURE COPPER.

  +---+-----+-----+-------+-------+---------+--------+--------+--------+
  |B. |Diam.|Diam.|Area in|Circum.| Pounds  | Feet   |  Feet  | Ohms   |
  |W. | in  | in  |Square |  in   |  per    |  per   |  per   |  per   |
  |G. | In. | mm. |Inches.|Inches.|  Mile.  | Pound. |  Ohm.  | 1000   |
  |No.|     |     |       |       |         |        |        | Feet.  |
  +---+-----+-----+-------+-------+---------+--------+--------+--------+
  | 1 |·3   |7·62 |·070686|·94248 |1444·0087|  3·662 |8706·843|  ·1148 |
  | 2 |·284 |7·21 |·063347|·89221 |1291·8699|  4·0988|7803·51 |  ·1282 |
  | 3 |·259 |6·58 |·052685|·81367 |1074·5697|  4·9262|6490·09 |  ·1540 |
  | 4 |·238 |6·04 |·044488|·74770 | 907·3683|  5·850 |5580·01 |  ·17007|
  | 5 |·22  |5·59 |·038013|·69115 | 773·045 |  6·83  |4681·1  |  ·2136 |
  | 6 |·203 |5·16 |·032365|·63774 | 657·205 |  8·02  |3985·7  |  ·2509 |
  | 7 |·180 |4·57 |·025447|·56549 | 517·493 | 10·20  |3134·8  |  ·3190 |
  | 8 |·165 |4·19 |·021382|·51836 | 434·861 | 12·14  |2633·7  |  ·3797 |
  | 9 |·148 |3·76 |·017203|·46495 | 349·853 | 15·10  |2119·9  |  ·4719 |
  |10 |·134 |3·40 |·014103|·42097 | 286·651 | 18·44  |1737·0  |  ·5757 |
  |11 |·120 |3·05 |·011309|·37699 | 229·997 | 22·95  |1392·9  |  ·7179 |
  |12 |·109 |2·77 |·009331|·34243 | 189·763 | 27·82  |1149·4  |  ·8700 |
  |13 |·095 |2·41 |·007088|·29845 | 144·144 | 36·63  | 873·1  | 1·1454 |
  |14 |·083 |2·11 |·005411|·26075 | 110·035 | 47·98  | 665·3  | 1·503  |
  |15 |·072 |1·83 |·004071|·22619 |  82·790 | 63·77  | 501·5  | 1·9941 |
  |16 |·065 |1·65 |·003318|·20420 |  67·478 | 78·25  | 408·7  | 2·4466 |
  |17 |·058 |1·47 |·002642|·18221 |  51·3163|102·89  | 310·8  | 3·2176 |
  |18 |·049 |1·24 |·001886|·15394 |  38·3486|137·68  | 232·3  | 4·3052 |
  |19 |·042 |1·07 |·001385|·13195 |  28·1741|187·40  | 170·6  | 5·8599 |
  |20 |·035 | ·89 |·000962|·10995 |  19·5677|269·83  | 118·5  | 8·4381 |
  |21 |·032 | ·81 |·000804|·10053 |  16·3574|322·79  |  99·1  |10·094  |
  |22 |·028 | ·71 |·000616|·08796 |  12·5242|421·58  |  75·8  |13·185  |
  |23 |·025 | ·63 |·000491|·07854 |   9·9845|528·82  |  60·5  |16·539  |
  |24 |·022 | ·55 |·000380|·06911 |   7·7299|683·06  |  46·8  |21·357  |
  +---+-----+-----+-------+-------+---------+--------+--------+--------+


ELECTRICAL RESISTANCE OF COPPER WIRE IN FRENCH MEASUREMENTS.

    +-------+------------+------+-------------+------------+----------+
    | B.W.G.|  Diameter  | Area |Circumference|  Metres    |   Kg.    |
    |  No.  |     in     |  in  |     in      |     per    |   per    |
    |       |Millimeters.|  mm. | Millimeters.| Kilogramme.|  Metre.  |
    +-------+------------+------+-------------+------------+----------+
    |   1   |   7.62     | 45.6 |    23.9     |    1ᵐ.95   | 0ᵏ.514   |
    |   2   |   7.21     | 40.8 |    22.6     |     2.78   |  0.360   |
    |   3   |   6.58     | 34   |    20.7     |     3.33   |  0.300   |
    |   4   |   6.04     | 28.7 |    19       |      3.95  |  0.253   |
    |   5   |   5.59     | 24.5 |    17.6     |      4.61  |  0.217   |
    |   6   |   5.16     | 21   |    16.2     |      5.43  |  0.184   |
    |   7   |   4.57     | 16.4 |    14.3     |      6.90  |  0.145   |
    |   8   |   4.19     | 13.8 |    13.1     |      8.20  |  0.122   |
    |   9   |   3.76     | 11.1 |    11.8     |     10.20  |  0.098   |
    |  10   |   3.40     |  9.1 |    10.7     |     12.50  |  0.080   |
    |  11   |   3.05     |  7.3 |     9.6     |     13.50  |  0.074   |
    |  12   |   2.77     |  6   |     8.7     |     18.87  |  0.053   |
    |  13   |   2.41     |  4.6 |     7.6     |     24.80  |  0.0403  |
    |  14   |   2.11     |  3.5 |     6.63    |     32.40  |  0.0309  |
    |  15   |   1.83     |  2.63|     5.75    |     45.10  |  0.0232  |
    |  16   |   1.65     |  2.14|     5.18    |     52.90  |  0.0189  |
    |  17   |   1.47     |  1.70|     4.62    |     69.40  |  0.0144  |
    |  18   |   1.24     |  1.21|     3.90    |     94.30  |  0.0106  |
    |  19   |   1.07     |  0.9 |     3.36    |    135.10  |  0.0074  |
    |  20   |   0.89     |  0.62|     2.80    |    181.8   |  0.0055  |
    |  21   |   0.81     |  0.51|     2.54    |    212.8   |  0.0047  |
    |  22   |   0.71     |  0.39|     2.23    |    285.7   |  0.0035  |
    |  23   |   0.63     |  0.31|     1.98    |    364     |  0.0028  |
    |  24   |   0.55     |  0.24|     1.73    |    465     |  0.00215 |
    +-------+------------+------+-------------+------------+----------+

    +-------+------------------------------+------------+--------+
    | B.W.G.|        Resistance in Ohms    | Kilogrammes| Metres |
    |  No.  +-----------------+------------+     per    |  per   |
    |       | per Kilogramme. | per Metre. |     Ohm.   |  Ohm.  |
    +-------+-----------------+------------+------------+--------+
    |   1   |    0.00073515   |  0.000377  |   1360     | 2652   |
    |   2   |    0.00116760   |  0.000420  |    860     | 2379   |
    |   3   |    0.00168165   |  0.000505  |    595     | 1980   |
    |   4   |    0.00232260   |  0.000588  |    430     | 1700   |
    |   5   |    0.00322700   |  0.000700  |    310     | 1430   |
    |   6   |    0.00452319   |  0.000833  |    220     | 1200   |
    |   7   |    0.00731400   |  0.00106   |    137     |  945   |
    |   8   |    0.01025000   |  0.00125   |     98     |  802   |
    |   9   |    0.01581000   |  0.00155   |     63     |  646   |
    |  10   |    0.0237500    |  0.00190   |     42.20  |  527   |
    |  11   |    0.0318600    |  0.00236   |     31.40  |  424   |
    |  12   |    0.0539682    |  0.00286   |     18.60  |  350   |
    |  13   |    0.0932480    |  0.00376   |     10.70  |  266   |
    |  14   |    0.160380     |  0.00495   |      6.26  |  202   |
    |  15   |    0.294954     |  0.00654   |      3.40  |  153   |
    |  16   |    0.430077     |  0.00813   |      2.30  |  123   |
    |  17   |    0.73564      |  0.0106    |      1.35  |   94.5 |
    |  18   |    1.33906      |  0.0142    |      0.75  |   70.4 |
    |  19   |    2.60743      |  0.0193    |      0.38  |   51.9 |
    |  20   |    5.05404      |  0.0278    |      0.20  |   36   |
    |  21   |    7.04368      |  0.0331    |      0.14  |   30.2 |
    |  22   |   12.37081      |  0.0433    |      0.08  |   23.1 |
    |  23   |   19.6924       |  0.0541    |      0.05  |   18.5 |
    |  24   |   32.5500       |  0.0700    |      0.03  |   14.3 |
    +-------+-----------------+------------+------------+--------+

          For Table of English Measurements see page 105.




EXPLANATION OF TERMS.


      _Accumulator._—Another name for secondary batteries.

      _Alternate Current Dynamo._—Produces currents which are
    alternately positive and negative.

      _Amalgamation._—Zinc is protected from local action by
    having its surface coated with mercury.

      _Ampère._—The Unit of current. A volt divided by an ohm.
    (See Electrical Measurements, page 104.)

      _Ampère Meter._—An instrument used for measuring strength
    of current.

      _Anode._—The positive electrode or pole of a decomposing
    cell, the wire or plate connected to the copper or other
    negative element of a battery. In electro-plating, it is
    usually the soluble pole of the metal to be deposited.
    (_v._ Cathode.)

      _Arc._—The air space in which the electric light forms.

      _Armature._—The keeper of a magnet: the part which closes
    the magnetic lines of the field-magnet, or the rotary part.

      _Battery._—A combination of two or more voltaic cells
    coupled together.

      _B. A._—British Association.

      _Block Station._—A central-station for the supply of
    continuous buildings.

      _Board of Trade Unit._—One thousand watt hours equals 10
    ampères at 100 volts per hour, or 1·35 HP. working for one hour.

      _Bobbin._—A coil of wire, or a number of such coils,
    generally so mounted that they can be rapidly revolved.

      _Bridge (Wheatstone’s)._—An apparatus for measuring
    resistances by balancing the unknown resistance against one
    known and capable of adjustment.

      _B. W. G._—Birmingham wire gauge.

      _Candle-Power._—Term used to denote the amount of
    light as compared with a standard sperm candle, which is
    a spermaceti candle, burning at the rate of 2 grains per
    minute.

      _Carbons._—The electrodes of arc lamps; the negative
    plate of a battery.

      _Carcel Lamp._—The French standard, equal to 9·4 candles.

      _Capacity_ (K).—The powder of a surface to hold
    electricity as “static charge.” A coulomb divided by a volt.
    Its Unit is the Farad.

      _Cathode._—The negative pole of a battery; the wire or
    plate connected with the zinc or positive element of the
    battery. The object on which a metallic deposit is to be
    formed. (_v._ Anode).

      _Centimetre._—The hundredth part of a metre.

      _Cell._—Each separate vessel in which a chemical action
    occurs, by which electricity is capable of being developed.

      _Central-station._—A building containing plant for
    supplying electricity to the public.

      _C. G. S._—The centimetre-gramme-second system.

      _Circuit Conductive._—The wires which form the path for
    the passage of the current.

      _Commutator._—A circuit changer, or switch. The collector
    of currents on a dynamo.

      _Compound Winding._—A method of increasing or decreasing
    the energy developed in a dynamo in proportion to the demand.

      _Conductivity._—Is the reciprocal to resistance, and
    applies to that property of any substance whereby the
    passage of electricity through it is effected with the least
    opposition.

      _Conductors._—Substances which most freely permit
    electricity to pass.

      _Connections._—Wires, &c., completing the circuit between
    different apparatus.

      _Contact Breaker._—The electric lighting equivalent for a
    gas tap.

      _Coulomb_ (Q).—The Unit of quantity, which passes in one
    second of an ampère current.

      _Cut-out._—An instrument placed in the circuit which will
    open it automatically.

      _Current_ (C).—The Unit is the Ampère. The supposed
    flow or passage of electricity or electrical force in the
    direction from + to -, or positive to negative.

      _Current Reverse._—A current in the opposite direction to
    the normal current.

      _Decimetre._—The tenth part of a metre.

      _Deflection._—The angle or number of degrees through
    which the needle of a galvanometer moves when a current is
    passing through its coils.

      _Diaphragm._—A porous division between two liquids
    through which electric current passes.

      _Duplex Cut-out._—An instrument which enables a spare
    fuse to be immediately substituted for that melted.

      _Duty._—A term used to denote the economy of any motor.

      _Dynamo._—A name given to machines which produce
    electricity for commercial purposes.

      _Dynamometer._—An instrument for ascertaining the
    horse-power absorbed by any machine.

      _Dyne._—The Unit of force which gives a velocity of 1
    centimetre per second to 1 gramme weight after acting for 1
    second.

      _Direct-Current Dynamo._—An electric generator producing
    currents passing in one direction.

      _Earth._—A term for the return circuit, which for economy
    is formed through the earth in telegraph work. A return
    conductor common to many circuits is sometimes called
    “earth.”

      _Electrodes._—A term for the poles or plates leading the
    current into and out of a cell.

      _Electrolysis._—The act of decomposition by the electric
    current.

      _Electrolyte._—The liquid in a cell.

      _Electrometer._—An instrument for measuring electric
    potential.

      _Electro-motive Force_ (_E. M. F._) (E).—The electric
    force tending to produce electric current. The Unit is the
    volt.

      _Erg._—The C. G. S. Unit of energy. The work of moving a
    body through 1 centimetre against the force of a dyne.

      _Extra Current._—The induced current of higher E. M. F.,
    which appears in a wire wound in a helix when the current is
    broken.

      _Farad._—The Unit of capacity: a coulomb divided by a
    volt.

      _Field of Force._—The space between or around the poles
    of a magnet.

      _Filament._—That part of an incandescent lamp which gives
    out the light.

      _Field-Magnets._—In a dynamo the magnets between which
    the armature revolves.

      _Foot Pound._—The British Unit of work, or 1 lb. raised 1
    foot high.

      _Galvanometer._—An instrument for measuring current.

      _Generator._—Another term for a dynamo.

      _Governor._—An apparatus for controlling the speed of any
    motor.

      _Horse-Power_ (_HP._)—indicated HP.—The Unit is 33,000
    lbs. lifted 1 foot high per minute. The nominal HP. of
    any motor is generally fixed considerably less than the
    indicated.

                                    2(A P R S)
          Ind. HP. of any engine =  —————————
                                     33,000

          A = Area of piston in square inches.
          P = Average pressure of steam in lbs. per square inch.
          R = Number of revolutions per minute.
          S = Length of stroke in feet (if in inches, × 33,000 by 12).

          The French “force cheval” represents 32,560 foot pounds.


      _Horse-Power of Water._—Indian Government rule, 15 cube
    feet per second falling through 1 foot = 1 HP.

      _Indicator Diagram._—The drawing produced by an
    instrument which is fixed to the cylinder of a steam-engine
    for the purpose of ascertaining its duty.

      _Induction._—The name given to effects produced out of a
    force-exerting body or out of the circuit to which the force
    is directly applied. A current in a wire induces currents in
    other conductors parallel to it.

      _Inertia._—The resistance to change of state of rest or
    motion.

      _Insulators._—Bodies possessing high electrical
    resistance. All insulating substances, however, allow some
    electricity to pass.

      _Intensity._—The old term for the properties now
    described as E. M. F. and potential.

      _Joule_, also called _Joulad_ (W).—The Unit of heat or
    work, it has also been applied to the mechanical equivalent
    of heat, 772 foot lbs.

      _Kilowatt._—One thousand watts.

      _Knot._—The geographical and nautical mile.

      _Leads._—Terms usually applied to copper conductors.

      _Magnetism._—A condition which can be highly developed in
    iron and steel, by electric action or otherwise.

      _Measurement._—See Units.

      _Metre._—The French standard of length = 3·28 feet.

      _Meg Ohm._—The prefix meg signifies a million.

      _Millimetre._—The thousandth part of a metre.

      _Milliampère._—The thousandth of an ampère.

      _Mica-foil._—The fusible portion of a Hedges cut-out.

      _Multiple Arc._—Galvanic cells or dynamos connected
    parallel, or lamps so arranged that each furnishes a
    separate path for the current.

      _Negative._—In a machine the wire returning from the
    lamp. In a galvanic battery the copper, carbon, or platinum
    plate. Sign -.

      _Nigger._—An American term used to denote an electrical
    fault.

      _Ohm._—The Unit of resistance. A volt divided by an
    ampère.

      _Ohm’s Laws._—Laws, investigated by Ohm, regulating
    electrical current magnitudes. Calling the current C,
    electro-motive force E, and resistance R: the expression is

      Current            E. M. F.            Resistance.
         E                                     E
    C = ——, amps.    E = C × R, volts.    R = —— ohms.
         R                                     C
              (See Electrical Measurements.)

      _Osmose._—The process of diffusion of liquids through a
    porous division.

      _Paraffin._—An insulating substance much used in
    telegraphic work.

      _Plummer Block._—The bearing on which a shaft revolves.

      _Polarity._—The distinct features of the two separate
    poles of a magnet.

      _Poles._—The two ends of a magnet. The wires, plates,
    &c., leading from a battery.

      _Positive._—In a machine the wire proceeding to the lamp.
    In a battery the zinc plate. Sign +.

      _Potential._—A word used to indicate a condition for
    work. Difference of potential is a difference of electrical
    condition. Potential of a battery means its E. M. F.

      _Power_ (P).—The rate of doing work. When an ampère
    passes through an ohm, the unit power, called a watt, is
    required.

      _Quantity_ (Q).—The Unit is the Coulomb.

      _Relay._—An electro-magnet which, receiving its current
    from a distance, closes the circuit of a local battery so as
    to produce the required effect of strength.

      _Resistance_ (R).—The opposition presented by the circuit
    to the development of the current. The Unit of resistance is
    the Ohm.

      _Rheostat._—An instrument for inserting resistances.
    A valuable artificial resistance employed for measuring
    unknown resistances.

      _Return Current._—The current in the wire leading to the
    machine.

      _Rigger._—The pulley or wheel by which power is
    transmitted.

      _Secondary Battery._—Wrongly termed an accumulator, is an
    appliance for storing energy in such a form that it shall be
    available for the reproduction of electric currents.

      _Secondary Generator._—A transformer of a current of high
    potential into a current of less E. M. F.

      _Series._—The plan of connecting lamps so that the
    current passes one after the other.

      _Shunt._—A coil of wire arranged to take a certain
    proportion of any current.

      _Solenoids._—Helices of wire which act like magnets.

      _Switch._—An apparatus for changing one circuit on to
    another.

      _Spectrum._—The elongated figure of the prismatic colours.

      _Torque._—Term used to express the strain on a shaft due
    to electro-magnetic action.

      _Units._—The various bases of any system of measurement.

      _Volt._—The Unit of electro-motive force and potential.
    An ampère multiplied by an ohm. (See Electrical
    Measurements.)

      _Voltameter._—An apparatus for measuring the current by
    its chemical action.

      _Voltmeter._—An instrument used for measuring E. M. F.

      _Watt._—The Unit of power. A volt-ampère. The horse-power
    electrical, taken as 746 B A watts, is equivalent to only
    736 true watts. The horse-power electrical is equal to 756
    B A watts, which is equal to 746 true watts. The “force de
    cheval,” or horse-power in use abroad, is defined as 75
    kilogrammetres, and is, therefore, 736 true watts.

      _Work_ (W.)—Is a volt multiplied by a coulomb, or
    (amp.² × sec × ohm) or (amp. × sec × volt). The Unit is the Joule.

      _Yoke._—Is a term applied to the apparently neutral mass
    of iron which connects the poles of a horse-shoe magnet at
    the back.

[Illustration]




APPENDIX I.—PRINCIPAL ELECTRIC LIGHTING STATIONS IN GREAT BRITAIN.


    -----------+--------------+-------------+-----------+-----------+
               | Approximate  |             |Approximate|           |
               |No. of Lights.|             | length of |           |
     Name of   +--------+-----+   Systems   |  longest  |   Main    |
     Station.  | Incan- |     |  employed.  |    main   | conductor |
               | descent| Arc.|             |   supply  |overhead or|
               | or Glow|     |             | conductor |underground|
               |  Lamps.|     |             | in miles. |           |
    -----------+--------+-----+-------------+-----------+-----------+
    Brighton   |        |     |High-tension |           |           |
    Electric-  |  1,800 |  40 |   lamps in  |    20     | Overhead  |
    Light      |        |     |   multiple  |           |           |
    Company    |        |     |series Brush |           |           |
               |        |     |   Dynamos   |           |           |
    -----------+--------+-----+-------------+-----------+-----------+
    Cadogan    |        |     |             |           |           |
    Electricity|        |     |   Edmunds’  |           |           |
    Supply     |   · ·  | · · |    system   |     2     | Overhead  |
    Company    |        |     | of Battery  |           |           |
    (New       |        |     |Transformers |           |           |
     Company)  |        |     |             |           |           |
    -----------+--------+-----+-------------+-----------+-----------+
               |        |     |Lowrie Hall  |           |  7 miles  |
    Eastbourne |  1,700 |  30 |Transformers |    15     |  under-   |
               |        |     |             |           |  ground   |
    -----------+--------+-----+-------------+-----------+-----------+
               |        |     |High-tension |           |           |
    Grosvenor  |        |     |with Ferranti|     6     |           |
    District   |        |     |Transformers | circuits, |           |
    Electrical | 20,000 |  40 |   primary   |  total    |           |
    Supply     |        |     | 2,400 volts,|  about    | Overhead  |
               |        |     |  secondary  | 70 miles  |           |
               |        |     |  200 volts, |           |           |
               |        |     |  Ferranti   |           |           |
               |        |     |   dynamos   |           |           |
    -----------+--------+-----+-------------+-----------+-----------+
    Kensington |        |     |   Crompton  |           |           |
    Court      | 1600   |     |  105 volts  |           |           |
    Electric   | to be  | · · | low-tension,|     ¼     |Underground|
    Lighting   |extended|     |   constant  |           |           |
    Company    |   to   |     |    supply   |           |           |
               | 10,000 |     | by means of |           |           |
               |        |     |accumulators |           |           |
    -----------+--------+-----+-------------+-----------+-----------+
               |        |     | Low-tension |           | Overhead  |
    Liverpool  |  1,000 | · · | continuous  |   · ·     |    and    |
               |        |     |  current    |           |Underground|
               |        |     |  dynamos    |           |           |
    -----------+--------+-----+-------------+-----------+-----------+
               |        |     | Chamberlain |           |           |
    Leamington |  1,500 | · · | and Hookham |           |Underground|
               |        |     |dynamos with |    1¼     |           |
               |        |     |accumulators |           |           |
    -----------+--------+-----+-------------+-----------+-----------+
    Paddington | 4,115  |  98 |  E. M. F.   |           |           |
    Electric   |16 C. P.|3,000| 150 volts,  |           |           |
    Lighting   |  lamps |C. P.|   Gordon    |     3     |Underground|
               |        |     |alternating  |           |           |
               |        |     |  current    |           |           |
               |        |     |   Dynamos   |           |           |
    -----------+--------+-----+-------------+-----------+-----------+

    -----------+--------------+--------+--------+------------+
               |              |        |        |            |
               |              |        |        |  Charges.  |
     Name of   | Approximate  |        |        |            |
     Station.  |    area of   |Working |Hours of+------------+
               | distribution.|Capital.|Supply. |            |
               |              |        |        | By Meter.  |
    -----------+--------------+--------+--------+------------+
    Brighton   |              |        |        |  Meter     |
    Electric-  |   About 3    |        |        |  rent,     |
    Light      |   square     | £12,000|Constant|21_s._ 8_d._|
    Company    |   miles      |        |        |    per     |
               |              |        |        |   annum    |
    -----------+--------------+--------+--------+------------+
    Cadogan    |              |        |        |            |
    Electricity|Belgravia and |        |        |            |
    Supply     |   Cadogan    |        |        |            |
    Company    |    Estate    | £20,000|   · ·  |    · ·     |
    (New       |              |        |        |            |
     Company)  |              |        |        |            |
    -----------+--------------+--------+--------+------------+
               |              |        |        |            |
    Eastbourne |    · ·       | £20,000|Constant|     · ·    |
               |              |        |        |            |
    -----------+--------------+--------+--------+------------+
               |Very irregular|        |        |            |
    Grosvenor  |   district,  |        |        |  7½ per    |
    District   |  a house is  |£375,000| 8 A.M. |  Board of  |
    Electrical |   lighted    |        |   to   |   Trade    |
    Supply     |   2 miles    |        | 3 A.M. |    unit    |
               |   station    |        |        |            |
               |   from the   |        |        |            |
               |   station    |        |        |            |
               |              |        |        |            |
    -----------+--------------+--------+--------+------------+
               | The streets  |        |        |            |
    Kensington |   adjoining  |        |        |  By meter  |
    Court      | the station, |        |        |and minimum |
    Electric   | the mains to | £25,000|Constant| charge of  |
    Lighting   | be continued |        |        | 10_s._ per |
    Company    | to another   |        |        |  light per |
               |  station at  |        |        |    annum   |
               |Knightsbridge |        |        |            |
    -----------+--------------+--------+--------+------------+
               |              |        |        |            |
    Liverpool  |              |        |        |  By meter  |
               |     · ·      |£20,000 |  · ·   | on sliding |
               |              |        |        |   scale    |
    -----------+--------------+--------+--------+------------+
               |              |        |        |            |
               |              |        |        |            |
               |              |        |        |            |
    Leamington |      183     |        |        |            |
               |     street   |   · ·  |Constant|            |
               |     lamps    |        |        |    meter   |
               |              |        |        |            |
    -----------+--------------+--------+--------+------------+
    Paddington |              |        |        |            |
    Electric   |              |        |        |            |
    Lighting   |   67 acres   |   · ·  |Constant|     · ·    |
               |              |        |        |            |
    -----------+--------------+--------+--------+------------+

    -----------+---------------------------------+---------------------+
               |                                 |                     |
               |             Charges.            |                     |
     Name of   |                                 |                     |
     Station.  |---------------------------------+     Remarks.        |
               |                                 |                     |
               |     By yearly fixed amount.     |                     |
               |                                 |                     |
    -----------+---------------------------------+---------------------+
    Brighton   | Glow lamps, 1_s._ per unit, or  | If consumption      |
    Electric-  |  rather over ¾_d._ per lamp     |     is below        |
    Light      | per hour. Arc lamps, 4_s_. per  |    100 units        |
    Company    |      lamp per week including    |    quarterly,       |
               |           maintenance           | 10¾_d._ discount.   |
    -----------+---------------------------------+---------------------+
    Cadogan    |                                 |                     |
    Electricity|                                 |                     |
    Supply     |                                 |                     |
    Company    |             · ·                 |         · ·         |
    (New       |                                 |                     |
     Company)  |                                 |                     |
    -----------+---------------------------------+---------------------+
               |  According to consumption       |      A similar      |
    Eastbourne |   averaging about 6½_d._        |       station       |
               |             per unit            |     at Hastings.    |
    -----------+---------------------------------+---------------------+
               |                                 |                     |
    Grosvenor  |                                 |                     |
    District   |                                 |    A station at     |
    Electrical |               · ·               |     Deptford is     |
    Supply     |                                 |    under erection   |
               |                                 |     to maintain     |
               |                                 |   200,000 lights.   |
               |                                 |                     |
               |                                 |                     |
    -----------+---------------------------------+---------------------+
               |                                 |                     |
    Kensington |8_d._ per unit, equal to 0·56_d._|                     |
    Court      |  per 20 C.-P. lamp per hour,    |  District embraces  |
    Electric   | or 0·28_d._ per 10 C.-P. lamp.  |  residences, shops, |
    Lighting   |  Shops taken at £2 per annum    |  public hall, and   |
    Company    |   per 20 C.-P. lamp minimum     |       church.       |
               |         of 10 lights            |                     |
               |                                 |                     |
    -----------+---------------------------------+---------------------+
               |                                 |   Board of Trade    |
    Liverpool  | First 400 hours, 1_s._ per unit |  license for six    |
               | Second  ”  ”     8_d._    ”     |years, hotels, shops,|
               | Afterwards       4_d._    ”     |   and residences.   |
    -----------+---------------------------------+---------------------+
               |   Street lights £2 2_s._ per    |                     |
               |      annum for 2,860 hours,     |                     |
               |        including renewals.      |                     |
    Leamington |1 to 40 units per quarter 8_d._  |                     |
               | per unit. 41 to 150 units per   |          · ·        |
               |  quarter, 6_d._ per unit. 151   |                     |
               |units per quarter 4_d._ per unit |                     |
    -----------+---------------------------------+---------------------+
    Paddington |                                 |The district between |
    Electric   |                                 |  Paddington and     |
    Lighting   |    Worked by G. W. Railway      |  Westbourne Park is |
               |                                 | lighted throughout. |
    -----------+---------------------------------+---------------------+

    --------------+-----------------+----------------+-----------+
                  |   Approximate   |                |Approximate|
                  |Number of Lights.|                | length of |
                  |-------+---------+                |  longest  |
       Name of    | Incan-|         |System employed.|   main    |
       Station.   |descent|   Arc.  |                |  supply   |
                  |or Glow|         |                | conductor |
                  | Lamps.|         |                |  in miles.|
    --------------+-------+---------+----------------+-----------+
    Barnet and    |       |         |                |           |
    District      |       |         |                |     5     |
    E. Supply     |  · ·  |   · ·   |  Joel Dynamos  |           |
    Company       |       |         |                |           |
    (New Company) |       |         |                |           |
    --------------+-------+---------+----------------+-----------+
    Chelsea       |       |         |                |           |
    E. Supply     |  · ·  |   · ·   |      · ·       |    · ·    |
    Company       |       |         |                |           |
    (New Company) |       |         |                |           |
                  |       |         |                |           |
    --------------+-------+---------+----------------+-----------+
    St. James     |       |         |                |           |
    and Pall      |  · ·  |   · ·   |   Continuous   |    · ·    |
    Mall          |       |         |    current     |           |
    (New Company) |       |         |                |           |
                  |       |         |                |           |
    --------------+-------+---------+----------------+-----------+
                  |       |         |    Thompson    |           |
                  |       |         |    Houston     |    · ·    |
    Taunton.      |  · ·  |   23    |   continuous   |           |
                  |       |         |    current     |           |
                  |       |         |                |           |
    --------------+-------+---------+----------------+-----------+
    Whitehall     |       |         |     Battery    |           |
    Court         |  · ·  |   · ·   |   Transformer  |    · ·    |
    (New Company) |       |         |     system     |           |
                  |       |         |                |           |
                  |       |         |                |           |
    --------------+-------+---------+----------------+-----------+
    Westminster   |  · ·  |   · ·   |      · ·       |    · ·    |
    --------------+-------+---------+----------------+-----------+
    West          |       |         |   Lowrie Hall  |  10 miles |
    Brompton      |  · ·  |   · ·   |   Transformers |    when   |
                  |       |         |                | completed |
                  |       |         |                |           |
                  |       |         |                |           |
    --------------+-------+---------+----------------+-----------+
    Adelphi       |       |         |   Continuous   |     12    |
    Theatre       | 4,000 |   · ·   |    current     |  external |
                  |       |         |    dynamos     |  circuits |
                  |       |         | coupled direct |           |
                  |       |         |   to engines   |           |
    --------------+-------+---------+----------------+-----------+
    Bath          |       |         |    Thomson     |           |
    (New Company) |  · ·  |   85    |    Houston     |    · ·    |
                  |       |         |  Dynamos and   |           |
                  |       |         |  Transformers  |           |
    --------------+-------+---------+----------------+-----------+

    --------------+---------+-----------------+--------+--------+
                  |  Main   |                 |        |        |
                  |conductor|                 |        |        |
                  |overhead |Approximate area |Working |Hours of|
       Name of    |or under-|of distribution. |Capital.| Supply.|
       Station.   | ground. |                 |        |        |
    --------------+---------+-----------------+--------+--------+
    Barnet and    |Overhead |                 |        |        |
    District      | chiefly |      · ·        | £5,000 |   · ·  |
    E. Supply     |         |                 |        |        |
    Company       |         |                 |        |        |
    (New Company) |         |                 |        |        |
    --------------+---------+-----------------+--------+--------+
    Chelsea       |         |                 |        |        |
    E. Supply     |   · ·   |      · ·        |   · ·  |   · ·  |
    Company       |         |                 |        |        |
    (New Company) |         |                 |        |        |
    --------------+---------+-----------------+--------+--------+
    St. James     |         |                 |        |        |
    and Pall      |   · ·   |      · ·        | £20,000|   · ·  |
    Mall          |         |                 |        |        |
    (New Company) |         |                 |        |        |
    --------------+---------+-----------------+--------+--------+
                  |         |                 |   · ·  |   · ·  |
    Taunton.      |Overhead | Street lighting |        |        |
    --------------+---------+-----------------+--------+--------+
    Whitehall     |         |    To light     |        |        |
    Court         |  · ·    |   hotels in     | £24,753|Constant|
    (New Company) |         | Northumberland  |        |        |
                  |         |     Avenue      |        |        |
                  |         |                 |        |        |
    --------------+---------+-----------------+--------+--------+
    Westminster   |   · ·   |      · ·        |   · ·  |   · ·  |
    --------------+---------+-----------------+--------+--------+
    West          |         |                 |        |        |
    Brompton      |   · ·   |      · ·        |   · ·  |Constant|
    --------------+---------+-----------------+--------+--------+
    Adelphi       |  Over-  |  The buildings  |        |        |
    Theatre       |  head   |   are close     | Private|   · ·  |
                  |   and   |    together     |        |        |
                  | under-  |                 |        |        |
                  | ground  |                 |        |        |
    --------------+---------+-----------------+--------+--------+
    Bath          |         |                 |        |        |
    (New Company) |   · ·   |   Arc lights    |   · ·  |   · ·  |
                  |         |   in streets    |        |        |
    --------------+---------+-----------------+--------+--------+

    -----------+----------------------------------+--------------------+
               |             Charges.             |                    |
               |                                  |                    |
     Name of   +-----------+----------------------+                    |
     Station.  | By Meter. |      By yearly       |       Remarks.     |
               |           |    fixed amount.     |                    |
    -----------+-----------+----------------------+--------------------+
    Barnet and |           |                      |      71 lamps in   |
    District   |    · ·    |         · ·          |   streets on posts |
    E. Supply  |           |                      |     12 ft. high.   |
    Company    |           |                      |                    |
   (New        |           |                      |                    |
      Company) |           |                      |                    |
    -----------+-----------+----------------------+--------------------+
    Chelsea    |           |                      |                    |
    E. Supply  |    · ·    |         · ·          |         · ·        |
    Company    |           |                      |                    |
    (New       |           |                      |                    |
      Company) |           |                      |                    |
    -----------+-----------+----------------------+--------------------+
    St. James  |           |                      |     Area to be     |
    and Pall   |    · ·    |         · ·          |      lighted       |
    Mall       |           |                      |     adjoining      |
    (New       |           |                      |      station.      |
      Company) |           |                      |                    |
    -----------+-----------+----------------------+--------------------+
    Taunton.   |    · ·    |  By yearly contract  |    Arc lamps of    |
               |           |                      |     1200-C.-P.     |
    -----------+-----------+----------------------+--------------------+
    Whitehall  | Proposed  |  Proposed charge,    |     Amalgamated    |
    Court      |  meter-   |  8_d._ per unit with |       with the     |
    (New       |   rent    |   minimum of £1. 1   |   Metropolitan     |
      Company) |10_s._ per |  per lamp per annum  |      Electric      |
               | quarter   |                      |   Supply Company.  |
    -----------+-----------+----------------------+--------------------+
    Westminster|    · ·    |         · ·          |     New Company.   |
    -----------+-----------+----------------------+--------------------+
    West       |  By meter | The station is being erected by the House |
    Brompton   |           |     to House Lighting Company, who also   |
               |           | propose installations in other districts. |
    -----------+-----------+-------------------------------------------+
    Adelphi    |    · ·    |   The Adelphi Theatre, Adelaide Gallery,  |
    Theatre    |           |      and Strand Restaurant are lit,       |
               |           |   the machinery being fixed in a basement |
               |           |    about 30 × 45 feet. No gas is laid on. |
    -----------+-----------+----------------------+--------------------+
    Bath       |           |                      | The power obtained |
    (New       |    · ·    |   Yearly contract    |    from town weir  |
      Company) |           |                      |     supplemented   |
               |           |                      |   by steam-engine. |
    -----------+-----------+----------------------+--------------------+




APPENDIX II.—PRINCIPAL ELECTRIC LIGHTING STATIONS ON THE CONTINENT.


    --------------+---------------------+----------------+-----------+
                  |     Approximate     |                |Approximate|
                  |  Number of Lights.  |                | length of |
                  +-----------+---------+                |  longest  |
       Name of    |   Incan-  |         |    System      |    main   |
       Station.   |  descent  |   Arc.  |   employed.    |  supply   |
                  |  or Glow  |         |                | conductor |
                  |   Lamps.  |         |                | in miles. |
    --------------+-----------+---------+----------------+-----------+
    Bergen        |  3,000    |   70    |     Brush      |    · ·    |
    --------------+-----------+---------+----------------+-----------+
    Bellegarde    |    600    |   · ·   | Gramme dynamos |    · ·    |
    --------------+-----------+---------+----------------+-----------+
    Berlin        | 11,800    |   · ·   |  Edison lamps  |    · ·    |
                  |           |         |    100 volts   |           |
      ”           | 17,400    |   · ·   |       ”        |    1½     |
      ”           |  3,000    |   108   |       ”        |    · ·    |
      ”           | 42,200    |   400   |       ”        |    · ·    |
    --------------+-----------+---------+----------------+-----------+
                  |           |         |                |           |
    Breslau       |  5,000    |   69    |     Siemens    |    · ·    |
    --------------+-----------+---------+----------------+-----------+
    Brunswick     |  2,000    |   · ·   |      Edison    |    · ·    |
    --------------+-----------+---------+----------------+-----------+
    Crefeld       |  1,560    |   · ·   |        ”       |    · ·    |
    --------------+-----------+---------+----------------+-----------+
    Darmstadt     |  1,000    |   · ·   |        ”       |    · ·    |
    --------------+-----------+---------+----------------+-----------+
    Dresden       |  3,400    |   · ·   |        ”       |    · ·    |
    --------------+-----------+---------+----------------+-----------+
    Elberfeld     |  2,000    |   · ·   |        ”       |    · ·    |
    --------------+-----------+---------+----------------+-----------+
    Hamburg       |  4,000    |   50    |    Schuckert   |    · ·    |
    --------------+-----------+---------+----------------+-----------+
    Hernösand     |  · ·      |   70    |     Thomson    |    · ·    |
                  |           |         |     Houston    |           |
    --------------+-----------+---------+----------------+-----------+
    Halle         |  1,350    |   10    |      Edison    |    · ·    |
    --------------+-----------+---------+----------------+-----------+
                  |  10,000   |         |                |           |
    Hanover       |   to be   |         |                |           |
                  | increased |   · ·   |        ”       |    · ·    |
                  |    to     |         |                |           |
                  |  20,000   |         |                |           |
    --------------+-----------+---------+----------------+-----------+

    ------------+---------+----------------+-----------------+--------+
                |  Main   |                |                 |        |
                |conductor|                |                 |        |
       Name of  |overhead |Approximate area|  Description    |Hours of|
       Station. |or under-|of distribution.|  of lighting.   | Supply.|
                | ground. |                |                 |        |
    ------------+---------+----------------+-----------------+--------+
                |         |                |    Street       |        |
    Bergen      | Overhead|       · ·      |   lighting      |   · ·  |
                |         |                |  and public     |        |
                |         |                |   buildings     |        |
    ------------+---------+----------------+-----------------+--------+
    Bellegarde  | Overhead|       · ·      |      · ·        |   · ·  |
    ------------+---------+----------------+-----------------+--------+
    Berlin      |  Under- |  Nearly whole  | These instal-   |        |
                |  ground |  of business   |    lations      |        |
                |         |  part of city  |    supply       |Constant|
      ”         |    ”    |                |    clubs,       | service|
      ”         |    ”    |                |   theatres,     |        |
      ”         |    ”    |                |    public       |        |
                |         |                |   buildings,    |        |
                |         |                |     and         |        |
                |         |                |street lighting  |        |
    ------------+---------+----------------+-----------------+--------+
                |  Under- |  1,200 metres  |    Railway      |        |
    Breslau     |  ground |     radius     |  station and    |   · ·  |
                |         |                |     mills       |        |
    ------------+---------+----------------+-----------------+--------+
    Brunswick   |    ”    |      · ·       |       · ·       |   · ·  |
    ------------+---------+----------------+-----------------+--------+
    Crefeld     |    ”    |      · ·       |   Mills and     |   · ·  |
                |         |                |   factories     |        |
    ------------+---------+----------------+-----------------+--------+
    Darmstadt   |    ”    |      · ·       |       · ·       |   · ·  |
    ------------+---------+----------------+-----------------+--------+
    Dresden     |    ”    |      · ·       |       · ·       |   · ·  |
    ------------+---------+----------------+-----------------+--------+
    Elberfeld   |  Under- |   Three-wire   |       · ·       |   · ·  |
                |  ground |     system     |                 |        |
    ------------+---------+----------------+-----------------+--------+
                |         |                | Lighting of the |  Dusk  |
    Hamburg     |    ”    |      · ·       |   Free Port     |  until |
                |         |                |                 |  dawn  |
    ------------+---------+----------------+-----------------+--------+
    Hernösand   | Overhead|      · ·       |       · ·       |   · ·  |
    ------------+---------+----------------+-----------------+--------+
    Halle       |  Under- |      · ·       |  Stadt Theatre  |   · ·  |
                |  ground |                |                 |        |
    ------------+---------+----------------+-----------------+--------+
    Hanover     |    ”    |   13,000 feet  | Shops and public|Constant|
                |         |     radius     |    buildings    |        |
                |         |   from station |                 |        |
    ------------+---------+----------------+-----------------+--------+

    --------------+------------------------------+--------------------+
                  |          Charges.            |                    |
                  +---------+--------------------+                    |
       Name of    |By Meter.|     By yearly      |      Remarks.      |
       Station.   |         |   fixed amount.    |                    |
    --------------+---------+--------------------+--------------------+
    Bergen        |   · ·   |       · ·          |        · ·         |
    --------------+---------+--------------------+--------------------+
                  |         |    Of fr. 0·4 per  |                    |
                  |         |  hour, or 8 francs |     Worked by      |
    Bellegarde    |   · ·   |    per month for   |    water power.    |
                  |         |      8-C.-P.       |                    |
    --------------+---------+--------------------+--------------------+
    Berlin        |         |6_s._ per year fixed|                    |
                  |         | charge, and ½_d._  | Stations at        |
                  |         |   per hour per     | Friedrich Street,  |
      ”           |   · ·   |  16-C.-P. lamp;    | Mauer Street,      |
      ”           |         |arc lamps, 6_d._ and| Schadou Street.    |
      ”           |         | 7_d._ per hour, and|                    |
                  |         |    60_s._ yearly   |                    |
                  |         |     per light      |                    |
    --------------+---------+--------------------+--------------------+
    Breslau       |   · ·   |        · ·         |        · ·         |
    --------------+---------+--------------------+--------------------+
    Brunswick     |   · ·   |        · ·         |        · ·         |
    --------------+---------+--------------------+--------------------+
    Crefeld       |   · ·   |        · ·         |        · ·         |
    --------------+---------+--------------------+--------------------+
    Darmstadt     |   · ·   |        · ·         |        · ·         |
    --------------+---------+--------------------+--------------------+
    Dresden       |   · ·   |        · ·         |        · ·         |
    --------------+---------+--------------------+--------------------+
    Elberfeld     |   · ·   |        · ·         |        · ·         |
    --------------+---------+--------------------+--------------------+
                  |         |                    | Under construction.|
    Hamburg       |   · ·   |        · ·         |  2 block stations, |
                  |         |                    |  1 central-station.|
    --------------+---------+--------------------+--------------------+
                  |         |                    |Yearly contract,    |
    Hernösand     |   · ·   |        · ·         | which is less than |
                  |         |                    | former lighting by |
                  |         |                    | oil.               |
    --------------+---------+--------------------+--------------------+
    Halle         |   · ·   |        · ·         |        · ·         |
    --------------+---------+--------------------+--------------------+
                  |By meter |                    |                    |
    Hanover       | to sub- |0·42_d._ per 10-    |                    |
                  | scribers| C.-P. lamp per     |        · ·         |
                  | for     | hour; 0·5_d._      |                    |
                  | three   | per 16-C.-P.       |                    |
                  | years   |                    |                    |
    --------------+---------+--------------------+--------------------+

    --------------+--------------------+--------------+-----------+
                  |    Approximate     |              |Approximate|
                  | Number of Lights.  |              | length of |
                  +--------------------+              |  longest  |
       Name of    |  Incan-  |         |    System    |    main   |
       Station.   | descent  |   Arc.  |   employed.  |  supply   |
                  | or Glow  |         |              | conductor |
                  |  Lamps.  |         |              | in miles. |
    --------------+----------+---------+--------------+-----------+
                  |          |         |Zippernowsky  |           |
    Lucerne       |      800 |   · ·   | high-tension |    4      |
                  |          |         | current with |           |
                  |          |         | transformers |           |
    --------------+----------+---------+--------------+-----------+
    Lubeck        |    2,000 |   · ·   |    Edison    |    · ·    |
    --------------+----------+---------+--------------+-----------+
                  |   11,000 |    210  |    Edison    |     ¾     |
    Milan         |          |         |              |           |
                  |    1,000 |   · ·   | Zippernowsky |     ”     |
    --------------+----------+---------+--------------+-----------+
    Munich        |    6,500 |    140  |    Edison    |     ”     |
    --------------+----------+---------+--------------+-----------+
    Rome          |   14,000 |   · ·   | Zippernowsky |     4     |
    --------------+----------+---------+--------------+-----------+
    Rotterdam     |    1,000 |   · ·   |    Edison    |    · ·    |
    --------------+----------+---------+--------------+-----------+
                  |          |         |Edison, Three-|           |
    St. Etienne   |    3,000 |   · ·   | wire system  |    · ·    |
    --------------+----------+---------+--------------+-----------+
                  |          |         |  Edison and  |           |
    Strassburg    |    1,800 |     62  |   Siemens    |    · ·    |
    --------------+----------+---------+--------------+-----------+
    Stuttgart     |    1,060 |   · ·   |      ”       |    · ·    |
    --------------+----------+---------+--------------+-----------+
    Schwerin      |    2,390 |   · ·   |      ”       |    · ·    |
    --------------+----------+---------+--------------+-----------+
                  |          |         |Goulard high- |           |
    Tivoli        |    1,000 |      6  |tension trans-|    18     |
                  |          |         |formers       |           |
    --------------+----------+---------+--------------+-----------+
    Tours         |    3,500 |   · ·   |    Goulard   |     3     |
    --------------+----------+---------+--------------+-----------+
    Terni         |    3,000 |   · ·   | Zippernowsky |    · ·    |
                  |          |         | Transformers |           |
    --------------+----------+---------+--------------+-----------+

    --------------+---------+----------------+---------------+--------+
                  |  Main   |                |  Description  |Hours of|
                  |conductor|  Approximate   |  of lighting. |Supply. |
                  |overhead |     area of    |               |        |
       Name of    |or under-|  distribution  |               |        |
       Station.   | ground. |                |               |        |
    --------------+---------+----------------+---------------+--------+
                  |         |To be extended  |               | Dusk   |
    Lucerne       |Overhead |  throughout    |  In hotels    |  until |
                  |         |   Lucerne      |               |  mid-  |
                  |         |                |               |  night |
    --------------+---------+----------------+---------------+--------+
    Lubeck        |    ”    |      · ·       |      · ·      |   · ·  |
    --------------+---------+----------------+---------------+--------+
                  |         |                |               |        |
                  |  Under- |1½ square mile  |The district is|        |
    Milan         |  ground |                | served in a   |Constant|
                  |         |Theatre with 460| similar manner|        |
                  |    ”    |lamps in houses | to gas        |        |
    --------------+---------+----------------+---------------+--------+
    Munich        |    ”    | Two theatres   |      · ·      |   · ·  |
    --------------+---------+----------------+---------------+--------+
                  |         |     Hotels     |               | 4 P.M. |
    Rome          |    ”    |      and       |      · ·      |   to   |
                  |         |     shops      |               | 1 A.M. |
    --------------+---------+----------------+---------------+--------+
    Rotterdam     |    ”    |      · ·       |      · ·      |   · ·  |
    --------------+---------+----------------+---------------+--------+
    St. Etienne   |    ”    |      · ·       |      · ·      |   · ·  |
    --------------+---------+----------------+---------------+--------+
                  | Under-  |Railway station,| Also a block  |  Dusk  |
                  |  ground | and goods      |  station for  |  until |
    Strassburg    |   and   | yards, 86 acres|  hotel and    |  day-  |
                  |  over-  | area           |  restaurants  |  light |
                  |  head   |                |               |        |
    --------------+---------+----------------+---------------+--------+
    Stuttgart     | Under-  |   Theatre      |      · ·      |   · ·  |
                  |  ground |                |               |        |
    --------------+---------+----------------+---------------+--------+
    Schwerin      |    ”    |      ”         |      · ·      |   · ·  |
    --------------+---------+----------------+---------------+--------+
                  |         | Principally    |               |        |
    Tivoli        | Overhead|   street       |      · ·      |   · ·  |
                  |         |   lighting     |               |        |
    --------------+---------+----------------+---------------+--------+
    Tours         |    ”    |      · ·       |      · ·      |   · ·  |
    --------------+---------+----------------+---------------+--------+
    Terni         |   · ·   | Town lighting  |      · ·      |   · ·  |
    --------------+---------+----------------+---------------+--------+

    --------------+-------------------------------+--------------------+
                  |          Charges.             |                    |
       Name of    +---------+---------------------+                    |
       Station.   |By Meter.|     By yearly       |      Remarks.      |
                  |         |   fixed amount.     |                    |
    --------------+---------+---------------------+--------------------+
    Lucerne       |   · ·   |        · ·          |Motive power, water.|
    --------------+---------+---------------------+--------------------+
    Lubeck        |   · ·   |        · ·          |         · ·        |
    --------------+---------+---------------------+--------------------+
                  | Arc and |Installation charge  |                    |
                  | incan-  |    per lamp         |                    |
    Milan         |descent  |per 10 candles, 8_s._|         · ·        |
                  |½_d._ per| ”  16   ”     28_s._|                    |
                  |ampère-  | ”  32   ”     56_s._|                    |
                  |hour     |   Arc lamp £2       |                    |
                  |         |  per annum rent     |                    |
    --------------+---------+---------------------+--------------------+
    Munich        |   · ·   |        · ·          |       · ·          |
    --------------+---------+---------------------+--------------------+
                  |         |  Of 2·08_d._        |The installation is |
    Rome          |   · ·   |   per 16 C.-P.      |  owned by the gas  |
                  |         |   lamp per hour     |      company.      |
    --------------+---------+---------------------+--------------------+
    Rotterdam     |   · ·   |        · ·          |         · ·        |
    --------------+---------+---------------------+--------------------+
                  |         |3_s._ 5_d._ per 16   |                    |
    St. Etienne   |  Meter  |C.-P. lamp per month,|         · ·        |
                  |         |also fixed sum of    |                    |
                  |         |2_s._ 11_d._ per lamp|                    |
    --------------+---------+---------------------+--------------------+
                  |         |Net cost of lighting |                    |
                  |         |station, including   |                    |
                  |         | 12 per cent. for    |Carried out by the  |
                  |         |interest and renewal.|railway company. The|
    Strassburg    |   · ·   |  —Arc lamps,        |cost is estimated at|
                  |         |3¾_d._ per hour;     |one-third less than |
                  |         |16 C.-P. glow lamps, |       gas.         |
                  |         |0·42_d._ per hour;   |                    |
                  |         |10 C.-P. glow lamps, |                    |
                  |         |0.32_d._ per hour; 8 |                    |
                  |         |C.-P. glow lamps,    |                    |
                  |         |0·29_d._ per hour    |                    |
    --------------+---------+---------------------+--------------------+
    Stuttgart     |   · ·   |        · ·          |One central-station.|
                  |         |                     | One block station. |
    --------------+---------+---------------------+--------------------+
    Schwerin      |   · ·   |        · ·          |         · ·        |
    --------------+---------+---------------------+--------------------+
                  |         |                     |Motive power, water;|
    Tivoli        |   · ·   |        · ·          | yearly contract for|
                  |         |                     | street lighting.   |
    --------------+---------+---------------------+--------------------+
                  |         |Subscribers at 2_s._ |Three distributing  |
    Tours         |   · ·   | 9_d._ per 16 C.-P.  | stations at work,  |
                  |         | lamp per month      | to be increased    |
                  |         |                     |      to ten.       |
    --------------+---------+---------------------+--------------------+
    Terni         |         |Charge 0·4_d._ to    |                    |
                  |   · ·   | 1·3_d._ per hour    |       · ·          |
                  |         | according to C.-P.  |                    |
    --------------+---------+---------------------+--------------------+

    --------------+---------------------+--------------+-----------+
                  |     Approximate     |              |Approximate|
                  |  Number of Lights.  |              | length of |
                  |---------------------+              |  longest  |
       Name of    |   Incan-  |         |    System    |    main   |
       Station.   |  descent  |   Arc.  |   employed.  |  supply   |
                  |  or Glow  |         |              | conductor |
                  |   Lamps.  |         |              | in miles. |
    --------------+-----------+---------+--------------+-----------+
    Treviso       |       800 |   · ·   | Zippernowsky |    · ·    |
                  |           |         | transformers |           |
    --------------+-----------+---------+--------------+-----------+
    Turin         |     1,000 |     100 |     Edison   |     · ·   |
    --------------+-----------+---------+--------------+-----------+
                  |           |         |    Brush     |           |
    Temesvar      |       760 |   · ·   |   machines;  |     2     |
                  |           |         |   Lane Fox   |           |
                  |           |         |    lamps     |           |
    --------------+-----------+---------+--------------+-----------+
                  |           |         |Crompton Low- |           |
                  |           |         | tension      |           |
    Vienna        |     8,000 |   · ·   | dynamos      |     ½     |
                  |           |         | with battery |           |
                  |           |         | transformers |           |
    --------------+-----------+---------+--------------+-----------+

    --------------+---------+-----------------+---------------+-------+
                  |  Main   |                 |               |       |
                  |conductor|   Approximate   |               |Hours  |
       Name of    |overhead |     area of     |  Description  |  of   |
       Station.   |or under-|   distribution  |  of lighting. |Supply.|
                  | ground. |                 |               |       |
    --------------+---------+-----------------+---------------+-------+
    Treviso       |Overhead |  Town lighting. |      · ·      |  · ·  |
    --------------+---------+-----------------+---------------+-------+
    Turin         | Under-  | Street lighting |      · ·      |  · ·  |
                  | ground  | by arc lamps    |               |       |
    --------------+---------+-----------------+---------------+-------+
                  |         |  About 37 miles |     Street    | Dusk  |
    Temesvar      |Overhead |  of streets     |    lighting   | until |
                  |         |                 |     chiefly   | dawn  |
    --------------+---------+-----------------+---------------+-------+
                  |         | Opera house,    |               |       |
    Vienna        | Under-  |  Court theatre, |      · ·      |  · ·  |
                  | ground  |  and municipal  |               |       |
                  |         |  buildings      |               |       |
    --------------+---------+-----------------+---------------+-------+

    --------------+----------------------------+---------------------+
                  |        Charges.            |                     |
                  +-------+--------------------+                     |
       Name of    |  By   |     By yearly      |      Remarks.       |
       Station.   | Meter.|   fixed amount.    |                     |
    --------------+-------+--------------------+---------------------+
    Treviso       |  · ·  |        · ·         |        · ·          |
                  |       |                    |                     |
    --------------+-------+--------------------+---------------------+
    Turin         |  · ·  |  Thomson-Houston   |        · ·          |
                  |       |     arc lamps      |                     |
    --------------+-------+--------------------+---------------------+
                  |       |  Street lighting,  |                     |
                  |       |  1·5 kreutzer      |                     |
                  |       |   per 16-C.-P.     |                     |
    Temesvar      |  · ·  |  lamp per hour     |        · ·          |
                  |       |                    |                     |
                  |       |Private consumers,  |                     |
                  |       |  1·81 kreutzer     |                     |
    --------------+-------+--------------------+---------------------+
                  |       |                    |This installation is |
                  |       | By contract at a   | being put down by   |
    Vienna        |  · ·  | price about double | the gas company     |
                  |       |      gas           | which lights the    |
                  |       |                    |     city.           |
    --------------+-------+--------------------+---------------------+




INDEX.


    Arc Lamps,
    —— places where suitable, 10.
    —— charges for, 10.
    —— at Milan, 47.
    Accumulators,
    —— at Kensington Court, 69.
    —— at Vienna, 76.

    Birmingham wire gauge resistance table, 105.
    —— in French measurements, 106.

    Central-stations,
    —— Siemens’ suggestion for, 1.
    —— at Philadelphia, 2.
    —— block, 3.
    —— construction, 3.
    —— selection of district for, 4.
    —— relation between daily output and capacity, 7.
    —— loss in, 15.
    —— at Deptford, 31.
    —— at Eastbourne, 31.
    —— at Brighton, 32.
    —— at Tours, 32.
    —— at Vienna, 76.
    —— position of, 16.
    —— in United States, 17.
    —— at Grosvenor Gallery, 27.
    —— Kensington Court, 20, 68.
    —— methods of lighting from, 20.
    —— tables showing cost of, 86, 87.
    Cost of gas compared with electricity, 8.
    Cost of kerosene, 9.
    Cost of arc lighting, 10.
    Conductors,
    —— relative size of, for different systems, 22.
    —— arrangement of, at Grosvenor Gallery, 28.
    —— primary conductors at Grosvenor Gallery, 30.
    —— diagram of network system of, at Milan, 46.
    —— diagram of multiple series system at Temesvar, 60.
    —— conduits for, in New York, 92, 93, 94.

    Distribution of Electricity,
    —— Edison parallel system, 41.
    —— Edison feeders, 42.
    —— three-wire system, 43.
    —— series system, 52.
    —— Bernstein system, 57.
    —— multiple series system, 58.
    —— by means of secondary batteries, 65.
    —— system of, at Kensington Court, 69.
    Dynamotors, 79.
    —— Swinburne’s Compound, 83.

    Electric Lighting,
    —— as an investment, 3, 9, 97.
    —— people who most readily take it up, 4.
    —— relation between number of lights used and number fixed, 4, 5.
    —— cost of, to householder, 5.
    —— diagram of, in London district, 6.
    —— diagram of, at Cincinnati, 7.
    —— charges for, 8.
    —— description of arc and glow, 9.
    —— at Tilbury Docks, 18.
    —— at Victoria Station, 18.
    —— at Paddington Station, 19.
    —— relative cost of, for direct and transformer systems, 21, 27.
    —— at Lucerne, 34.
    —— at Milan, 34, 44.
    —— cost of, at Milan, 48.
    —— at Berlin, 52.
    —— cost of, at Berlin, 53.
    —— Bernstein system of, 55.
    —— diagram of, system at Colchester, 67.
    —— working cost of, at Athenæum Club, 88.
    —— working cost of, at Naval and Military Club, 89.
    —— working cost of, at South Kensington Museum, 89.
    —— working cost of Thomson-Houston system of,
          in an American city, 90.
    Experiment at the Teatro dal Verone, 34.

    Faults, discovery of, 51.

    Gas Lights,
    —— heat from, advantages and objections, 3.
    —— number used and fixed, 4.
    —— cost of, at Berlin, 53.
    —— cost of, to householder, 5.
    Glossary, 107.

    Incandescent Lamps,
    —— number obtained per electrical HP., 8.
    —— illustration of, 11.
    —— candle-power of, 11.
    —— consumption of energy in, 10, 63.
    —— life of, 11.
    —— blackening of, 12.
    —— at Temesvar, 63.
    Lighting,
    —— number of hours of, per annum, 4.
    —— cost of, to London householder, 5.
    —— diagram of, in London district, 6.
    —— diagram of, at Cincinnati, 7.
    —— diagram of, 13.
    —— relative cost of, with direct and transformer system, 22.
    —— relative cost of, by electricity and gas, 91.
    Lucigen light, the, 99.
    —— cost of working, 100.

    Machinery at Grosvenor Gallery, 29.
    Motors, Electric, 39.
    —— diagram showing power supplied to, in Boston, 40.
    —— purposes used for, in America, 39.
    Meters, Electric,
    —— the Edison, 49.
    —— the Aron, 54.
    Mackenzie’s conduits for electric light cables, 95.

    Priestman’s petroleum engine, 98.

    Regulation of E. M. F. at Grosvenor Gallery, 29.
    Regulation of E. M. F. at Milan, 44.
    Rent of meters at Milan, 49.
    Rent of meters at Berlin, 53.
    Regulators for secondary batteries, 76.
    Resistance of Copper Wire, 105, 106.

    Speed indicators at Grosvenor Gallery, 29.
    Safety fuses at Grosvenor Gallery, 31.
    Safety fuses at Milan, 47.
    Switch, double pole, 72.

    Table I. showing cost of laying conductors, 74, 75.
    Table II. showing cost and maintenance of plant, 86, 87.
    Table showing resistance, &c., of copper wire, 105, 106.
    Table showing principal electric lighting stations
          in Great Britain, 116-119.
    Table showing principal electric lighting stations
          on the Continent, 120-125.
    Terms, explanation of, 107-115.
    Transformers,
    —— application of, 27.
    —— diagram of Ruhmkorff type of, 23.
    —— description of Ruhmkorff type of, 23.
    —— arrangements of circuits of, 24.
    —— two classes of, 24.
    —— Kapp & Snell, 27.
    —— distribution of electricity by means of, 21.
    —— prevention of shocks from, 30.
    —— Westinghouse converters, 35.
    —— potential used in, 38.
    —— direct current, 79.
    —— comparison between alternate and direct current, 80.
    —— Swinburne’s dynamotor, 83.
    —— advantages of Zippernowsky-Deri system of, 34.
    Turbines working the dynamos at Tivoli, 32.
    Turbines working the dynamos at Lucerne, 33.

    Useful Notes, 101-103.
    —— incandescent lights, 102.
    —— arc lighting of works, 102.
    —— approximate cost, 102.
    —— wire running, 103.
    —— Electrical Measurements, 104.

    Westinghouse system, 35.
    —— at Pittsfield, 37.
    Wires overhead or underground, 91.

                            [Illustration]


         LONDON: PRINTED BY WILLIAM CLOWES AND SONS, LIMITED,
                  STAMFORD STREET AND CHARING CROSS.




                                  THE

                            HOUSE-TO-HOUSE

                    Electric Light Supply Co., Ld.

         (MODEL CENTRAL ELECTRIC LIGHTING STATION, KENSINGTON,
              ADJOINING THE WEST BROMPTON STATION ON THE
                    METROPOLITAN DISTRICT RAILWAY)

                 _Are prepared to assist the formation
                                  of_

                    LOCAL ELECTRIC LIGHT COMPANIES,

                            _and to erect_

                           CENTRAL-STATIONS

                _for the distribution of Electricity in
                       any part of the Kingdom_.

                 Estimates for Complete Sets of Plant
                       furnished free of charge.

                      WILLIAM LOWRIE, _Engineer_.

                  H. St. JOHN WINKWORTH, _Secretary_,
                   117, Bishopsgate Street, London,
                                 E.C.


                      _BY THE SAME AUTHOR._
               PRECAUTIONS TO BE ADOPTED ON INTRODUCING

                          THE ELECTRIC LIGHT.
                     _INSURANCE RULES, &c._,
                                 WITH
       NOTES ON THE PREVENTION OF FIRE RISKS.

            _Illustrated._ Price 2_s._ 0_d._

                       THE SUPPLY OF ELECTRICITY
                         BY LOCAL AUTHORITIES.

                Demy 8vo. Illustrated. Price 1_s._


                     DISTRICT ELECTRICITY SUPPLY.

                   CENTRAL SUPPLY STATIONS WORKED ON
                              THE E.P.S.
               AUTOMATIC SYSTEM FOR THE PUBLIC SUPPLY OF
                           ELECTRICITY FROM
                          STORAGE BATTERIES.

                      Descriptive Pamphlet Free.


                        EPITOME OF THE SYSTEM.

                    The generating plant is all placed in a
                    conveniently situated building within
                    or without the District to be Lighted.

                    Convenient Sub- or Storage-Stations
                    are selected throughout this District,
                    and contain sufficient Accumulators to
                    supply the maximum demand.

                    The Batteries in each of these
                    Storage-Stations are recharged
                    in series, _one-half at a time_,
                    throughout the System during the period
                    of minimum demand, and by the evening
                    are all full and ready to cope with the
                    heavy night work.

                    The whole of the charging, discharging,
                    and regulating apparatus is worked
                    automatically.


                      ADVANTAGES OF THE SYSTEM.

                    =_Reliability._=—The Light is
                    solely derived from Storage, and
                    is absolutely steady. There is no
                    connection whatever between the Lamp
                    and Moving Machinery.

                    The Supply is continuous day and night.

                    =_Economy in Prime Outlay._=—The
                    proportion of Engine Power in use to
                    the power required for maximum supply
                    is only about _one- third_, while any
                    system, if running direct, requires
                    a large portion of the plant to be
                    duplicated.

                    =_Economy in Working._=—The
                    generating station is only at work a
                    definite number of hours during the
                    daytime, after which period the plant
                    may be let out or utilized for other
                    purposes, such as motive power, &c.

                    =_Electro Motors_= for all
                    purposes can be driven from the
                    ordinary discharge mains. This is
                    impossible where alternating currents
                    are employed.

    =GUARANTEE.=—The E.P.S. Co. undertake to supply
        all the necessary renewals for the Storage
        Batteries in use in the above system at the rate of
        =12=% per annum on the actual first cost of
        the Batteries.

    E.P.S. Accumulators are already in use at the
        following Central-Stations:—Vienna; Berlin;
        Cadogan (London); Norwich; Taunton; Leamington;
        St. Austell; Detroit, U.S.A.; Allentown, U.S.A.;
        Blenheim, U.S.A.; Haverford, U.S.A.; Delaud, U.S.A.

             _Districts Surveyed, Plans, Specifications
                   and Tenders submitted by the_
                ELECTRICAL POWER STORAGE COMPANY, LTD.,
                4 GREAT WINCHESTER STREET, LONDON, E.C.

  TELEGRAMS, “STORAGE, LONDON.”      TELEPHONE NO. 338.




                            ANGLO-AMERICAN
                Brush Electric Light Corporation, Ltd.

                           MANUFACTURERS OF
                  _BRUSH ARC DYNAMOS AND LAMPS._
               Victoria Incandescence Dynamos and Lamps.
                  ALTERNATE CURRENT DYNAMO MACHINES.
                         Transformers. Motors.
     _ALL FITTINGS FOR ARC AND INCANDESCENCE LIGHTING, Etc._

                            CONTRACTORS FOR
               PRIVATE INSTALLATIONS OF ELECTRIC LIGHT.
                   CENTRAL ELECTRIC LIGHT STATIONS.
                  _INSTALLATIONS ON SHIPBOARD._
                   ELECTRICAL RAILWAYS AND TRAMWAYS.
                Railway Train Lighting by Electricity.
                   INSTALLATIONS FOR TRANSMISSION OF
                           POWER, Etc. Etc.

      The Corporation are prepared to undertake the
    establishment of Central Electric Lighting Stations on the
    high or low-tension continuous current systems, with or
    without accumulators, or on the alternating current system
    with transformers, as may be best suited to the requirements
    of each particular case.

      The Corporation invite enquiries from Municipalities,
    Local Gas or Electrical Companies, or owners of Blocks of
    Houses or Shops, for the erection of Central Generating
    Stations, and the supply of Electricity, either on their own
    account, or upon such terms and conditions as may be agreed
    upon.

      Full particulars on application to—

                            THE SECRETARY,
                       112, BELVEDERE ROAD, LONDON, S.E.




                                UNITED

                        ELECTRICAL ENGINEERING

                           COMPANY, LIMITED.


      The company have exceptional facilities for carrying out
    contracts at home or abroad in the various branches of
    Electrical Engineering. They own several valuable patents in
    connection with the =distribution of Electricity and its
    application to industrial and domestic purposes=; they
    are not, however, restricted to any special system, and give
    particular attention to providing those appliances which are
    best adapted to the purposes in view.

      =The Works= are equipped for =manufacturing,
    testing, and repairing, and form a valuable auxiliary to
    extensive contract work=, enabling the Company to give
    prompt attention to the demands of their clients.


                            Contractors for

                    CENTRAL ELECTRIC
                                SUPPLY STATIONS.

                    ELECTRIC LIGHT INSTALLATIONS.

                    TRANSMISSION OF POWER.

                    THE “TELPHER” SYSTEM
                              OF CHEAP TRANSPORT.

                    ELECTRIC TRAMS & RAILWAYS, &c.

                 _Please apply for complete list of
              Electric Light and Power Supplies to_—
              =36, ALBERT EMBANKMENT, LONDON, S.E.=




                        CARBON WORKS, BARNSLEY.

                       THE GLOBE ELECTRICAL AND
                         ENGINEERING COMPANY.

                   ELECTRICAL AND GENERAL ENGINEERS.

                            [Illustration]

               _Contractors for Electric Lighting._

           _And Manufacturers of Dynamos, Lamps, Switches,
               Cut-outs, and every Appliance used in the
                  Installation of Electric Light._

      NO. 1 DEPARTMENT comprises all Electric Light
    Fittings, also Ornamental Electroliers, Pendants, Brackets,
    Ceiling Plates, or Rosettes, Globe Lamps and Globe Lamp
    Holders, also Glass Shades and Fringes in coloured glass of
    many varieties.

      NO. 2 DEPARTMENT. This includes the well known
    brand of Globe Carbon Rods and Battery Plates, Galvanic
    Batteries of all descriptions, Battery supplies or materials
    such as terminals, zinc, crushed carbon, chemicals, jars,
    and porous pots. Measuring Instruments, Galvanometers,
    patent Speed Gauges, Ammeters and Voltmeters—the accuracy
    of same certified and laboratory test supplied.

      NO. 3 ELECTRICAL ENGINEERING. Dynamos,
    Alternating and Continuous Current. Transformers,
    Cable—plain, copper, lead coated; also of _the special
    high insulation_ required by London Electrical Supply
    Co.’s rules. Sundries for Central-Station Installation.
    Special List will be sent on application. Telephones and
    Transmitters. Sundries for Telephone Installations.

 _Belting, Oils, Waste, Paint, Patent Jointing Mastic, &c., are kept
        in Stock, also Cable, Silk and Cotton Covered Wire._

        Address:—=The MANAGER=,
                Offices—=7, CARTERET STREET=.

     _Supply Stores: 20, Dartmouth Street, Westminster, S.W._
               Telegraphic Address, “Globulous, London.”




                        CARBON WORKS, BARNSLEY.

                                  THE
                Globe Electrical & Engineering Company.

                     CARBON CUTTERS AND GRINDERS.

                             CARBON RODS.

                            [Illustration]

                            CARBON PLATES.

      =ELECTRIC LIGHT CARBON RODS= (Fig. 6), cored and
    solid, coppered and plain. All sizes in stock from 4 to 40⁽ᵐᵐ⁾.}
    Makers of Sir James Douglas’s Rods (Fig. 4), as used by
    the Trinity House.

      =CARBON PLATES= for Leclanché Batteries, etc. (Fig. 3),
    Consolidated Battery Plates, made to withstand nitric
    acid or bichromate, can be supplied up to 13ins. + 10ins.
    out of stock, and larger sizes to order.

      =CARBON CELLS AND CYLINDERS= (Figs. 1, 2, and 5), of
    all descriptions.

     Experimental Carbon Goods of every description made to Order.

                        PRICES ON APPLICATION.
      _Offices_:—=7, CARTERET ST., WESTMINSTER, S.W.=




                              THE GULCHER
                   ELECTRIC LIGHT & POWER CO., LTD.,
              BATTERSEA FOUNDRY, BATTERSEA, LONDON, S.W.

                 Manufacturers of Electrical Machinery
                         OF EVERY DESCRIPTION.

            Contractors to H.M. NAVY, H.M. WAR DEPARTMENT,
                      Sir W. G. ARMSTRONG & CO.,
              OUDH AND ROHILKUND RAILWAY CO., etc., etc.

                            [Illustration]


    THE COMPANY SUPPLY—
         =DYNAMOS.= Series, Shunt, and Compound Wound.
         =ARC LAMPS.= Projectors, Search Lights, etc.
         =SWITCH BOARDS= and Fittings.
         =ALTERNATING CURRENT DYNAMOS.=
         =TRANSFORMERS.=
         =SECONDARY BATTERIES.=

    =COMPLETE INSTALLATIONS= for lighting =TOWNS=,
      =PUBLIC BUILDINGS=, =MILLS=, =FACTORIES=,
      =IRONWORKS=, and =COLLIERIES=, also =PRIVATE
      HOUSES= and =MANSIONS=.

    _SOLE CONTRACTORS for the PERMANENT LIGHTING of the CRYSTAL
      PALACE, Sydenham, and the ROYAL AQUARIUM, WESTMINSTER,
      also the CITY of WELLINGTON, New Zealand._




                          WOODHOUSE & RAWSON,
                               LIMITED.

                 Electrical Engineers and Contractors,
                                FOR THE
             LIGHTING OF CITIES, TOWNS, FACTORIES, MILLS,
                                  AND
                          PRIVATE RESIDENCES.

                    COMPLETE CENTRAL-STATION PLANT.

           Houses Wired and Fitted throughout for connection
                     to Central-Station Circuits.

   ESTIMATES ON APPLICATION. GOOD WORK AT MODERATE PRICES.

            =11, QUEEN VICTORIA STREET, LONDON, E.C.=

       _Contractors to the Chief Exhibitions, Stock Exchange,
            Messrs. W. H. Smith & Sons, Peak, Frean & Co.,
          Crosse & Blackwell, Grosvenor Gallery, &c., &c._




                                  THE
                     Orient Electric Light Company
                               LIMITED.

                            [Illustration]

     _Contractors for the supply of Electric Lighting Plant for
       Private Houses, Public Buildings, Factories, Towns, &c.,
         on the most approved system and at moderate cost._

             QUOTATIONS GIVEN FOR TEMPORARY INSTALLATIONS.

             Central-Stations Fitted Out, and Negotiations
                         carried on for same.

                    ESTIMATES AND QUOTATIONS FREE.

              London Offices: 2, East India Avenue, E.C.

                        AGENTS ABROAD:

     Messrs. GILLANDERS, ARBUTHNOT & CO.      Calcutta and Rangoon
     Messrs. GORDON, WOODROFFE & CO.          Madras.
     Messrs. EWART, LATHAM & CO.              Bombay.




_Crown 8vo., 128 pp., Limp cloth, 40 Illustrations. Price 2s. 6d._

               PRECAUTIONS TO BE ADOPTED ON INTRODUCING
                          THE ELECTRIC LIGHT.

              WITH NOTES ON THE PREVENTION OF FIRE RISKS.

      CONTENTS.—_Fire Risk Committee—Resistance of
    Conductors—Glow Lamps—Sizes of Main and Branch
    Conductors—Standard and Birmingham Wire Gauge—Factors
    for Calculation—Running of Wires—Switches—Connectors
    and Joints—Insulators—Short Circuit—Cut-out, Fusible,
    and Automatic—Lamp Holders—Life of Lamps, Electrical
    Governor, Speed Gauge—Testing Insulation—Fires and
    Accidents from Electric Current—Specification for
    Electric Lighting—Instructions for Working—Phœnix
    Fire Office Rules—American Fire Office Rules—Electrical
    Measurements—Resistance of Copper and German
    Silver—English and French Measure—Rules for Fusible
    Mica-Foils—Rules for Direction of Current—Number of
    Electric Lights to compare with Gas—Motive Power, Steam,
    Gas—Motive Power, Water—Explanation of Terms—Price List._

                        OPINIONS OF THE PRESS.
                          _The Builder._

      “Mr. Hedges points out clearly the risks that are
    inseparable from slovenly work and incompetent handling,
    and gives clear directions for carrying the main and branch
    conductors and the lamp wires, and for calculating the sizes
    of the various leads according to the number of lights to be
    worked. He insists very properly that some regular system
    should be followed, so that it should always be known which
    is the positive and which the negative wire,—in other
    words, which wire leads from the machine to the lamps, and
    which is the return. In addition, however, to showing this
    by mere position, _i.e._, by placing the positive wire on
    the left side of the negative if vertical, and under it if
    horizontal, we should strongly recommend that the insulating
    covering should be of different colours on the two wires,
    and thus any accidental displacement would not be of
    consequence.”

             _Revue Internationale de l’Electricité._

      “Ce petit livre sans prétention contient une grande
    quantité de renseignements pratiques. Tous ceux qui
    s’occupent d’éclairage électrique trouveront grand profit à
    le consulter.

      “Dans les quatre-vingts pages que contient ce travail,
    l’auteur a su rassembler toutes les indications nécessaires
    et utiles pour effectuer les installations. Il n’était pas
    possible de grouper d’une manière plus logique, plus claire
    et plus concise les règles à suivre pour assurer le bon
    fonctionnement d’une installation d’éclairage.

      “L’auteur s’est étendu surtout sur la description et
    l’installation des appareils de sùreté, sur la pose des
    conducteurs et sur les diamètres à leur donner, sur l’essai
    des circuits, etc....

      “Un petit dictionnaire, donnent l’explication des terms
    techniques, complète d’une manière heureuse ce petit guide
    qui sera consulté avec autant de profit que bien d’autres
    ouvrages plus étendus et conçus dans un esprit moins
    pratique.
                                           “AUG. M.”

            _Copies of the above can be obtained from_

             The Globe Electrical and Engineering Company,
                 7, CARTERET STREET, WESTMINSTER, S.W.
                 Manufacturers of Electrical Supplies.




                  E. AND F. N. SPON, LONDON.
            _Crown 8vo. 156 pp. Cloth gilt. Price 3s._

               Useful Information on Electric Lighting.
                             EMBODYING THE
               RULES OF THE FIRE RISK COMMITTEE AND THE
                        ELECTRIC LIGHTING BILL;

                                 ALSO
        PLAIN DIRECTIONS FOR THE WORKING OF ELECTRIC LAMPS
                       AND DYNAMO MACHINES.

                   BY KILLINGWORTH HEDGES,
         _M.I.C.E., M. Soc. Telegraph Engineers, F.C.S._

      _CONTENTS.—Introductory Remarks—The Production of
    Electricity—The Voltaic Arc—Division of the Electric
    Light—Machines or Generators—Power required, and
    Motors—Application of the Electric Light—Choice of a
    System—Electrical Measurement—Cost of Working—Result
    of Various Installations—Measurement of Light and
    Current—Storage of Electricity and Transmission of
    Power—Conclusion—Useful Tables and Memoranda._

                          _The Graphic_,

      “At the present time, when the question of illumination
    by electricity is fully under discussion, a third edition
    of Mr. Killingworth Hedges’ _Useful Information on Electric
    Lighting_ is doubly welcome. The little work is now fully
    brought up to date, and gives a plain, straightforwardly
    written account of the various forms of the arc and
    incandescent lamps, and, indeed, of the general system of
    electric lighting. Thus a very fair idea of the principle
    may be gathered by the general reader, who will find it a
    welcome companion when visiting the Electrical Exhibition,
    while the manufacturer in search of a practicable light for
    his workshop will gain valuable information from the various
    hints conveyed in its pages. To the scientific student also
    the work will be exceedingly useful, if only from the handy
    memoranda and tables in the appendix. _Altogether the book
    is the best of the kind that we have yet seen_, and we
    cannot refrain from hoping that Mr. Killingworth Hedges may
    see fit to bring out a more compendious and detailed work
    on the subject, with which he is so eminently competent to
    deal.”

                _Also, by the same Author, demy 8vo.
               Illustrated, 32 pp. Paper. Price 1s._

            The Supply of Electricity by Local Authorities.
    READ AT THE ANNUAL MEETING OF THE ASSOCIATION OF MUNICIPAL
              ENGINEERS AND SURVEYORS, OXFORD, 1883.

      All Mr. Hedges’ books are sent post free on receipt of
    postal order, by the GLOBE ELECTRICAL AND ENGINEERING
    COMPANY, Supply Stores, 7, Carteret Street, Westminster, S.W.




                                  THE
                               BARNSLEY
                            CARBON COMPANY.

                      Wholesale Manufacturers of

                     PURE CARBON POINTS, CANDLES,
               AND BATTERY PLATES OF EVERY DESCRIPTION.
                     CARBON CUTTERS AND GRINDERS.

                             CARBON WORKS:
                         =BARNSLEY,
                                YORKSHIRE=.

                            LONDON OFFICE:
                      7, Carteret Street,
                               Westminster, S.W.




                          J. EDMUNDSON & CO.,
                               LIMITED,
                       Engineers & Electricians,

                19, GREAT GEORGE ST., WESTMINSTER, S.W.

                     Electric Lighting for Country
                        and Town Mansions, &c.

      =J. EDMUNDSON & CO.=, invite an inspection of their
    Complete System of Lighting COUNTRY and TOWN
    MANSIONS, by means of Incandescent Electric Lights.

      =A COMPLETE INSTALLATION= consisting of =DYNAMO
    MACHINE=, =ENGINE=, =STORAGE BATTERY and
    LAMPS=, may be seen working at J. E. & Co.’s =SHOW
    ROOMS, 19, GREAT GEORGE STREET, WESTMINSTER=, where
    all information, including Estimates of Cost, &c., may be
    obtained.

        ESTIMATES ALSO GIVEN FOR TEMPORARY LIGHTING BY MEANS OF
             STORAGE BATTERIES, FOR BALLS, RECEPTIONS, &c.

                          SPECIAL AGENTS FOR
                         EDISON & SWAN LAMPS.

                      Special Terms to the Trade.

           MANUFACTURERS OF ELECTROLIERS, BRACKETS,
                                  AND
             All Descriptions of Electric Light Fittings.




                       Central-Station Lighting.

                            [Illustration]

                     _THE KAPP TRANSFORMER._

                             THE CONNAUGHT
                      alternating current Dynamo.
                           (KAPP’S PATENT.)

                            SHARP AND KENT,
                      ENGINEERS AND ELECTRICIANS,
      _Connaught Mansions, Victoria St., Westminster, S.W._

    TELEGRAPHIC ADDRESS—
    “=MEGAVOLT, LONDON.=”          =TELEPHONE, 3,125=




                     DR. ARONS ELECTRICITY METERS

      For Alternate and Continuous Current. Used in all the most
               Important Central-Stations in the World.

                            [Illustration]

                       THE GENERAL ELECTRIC CO.,
        (G. BINSWANGER & CO.) _Manufacturers and Suppliers of_

             The APOSTLE Carbons. | China and Glass Ware,
                 Switches, Lamps, Cables, Casings, &c.

          _The best without exception._| _In great variety_.
               Electrical Fittings of every description.

                               =LONDON=:
                       THE GENERAL ELECTRIC CO.,
                     5, GREAT ST. THOMAS APOSTLE,
                             LONDON, E.C.
                      _Telegrams: “Electricity.”_
                         _Telephone: “1887.”_

                             =MANCHESTER=:
                    MANCHESTER ELECTRIC WORKS CO.,
                 (G. BINSWANGER, _Managing Director_),
                      45, CHAPEL STREET, SALFORD,
                              MANCHESTER.
                       _Telegrams: “Induction.”_




                       THE GLOBE ELECTRICAL AND
                         ENGINEERING COMPANY.

      _Offices_:—=7, CARTERET ST., WESTMINSTER, S.W.=

                           MANUFACTURERS OF
              HEDGES’ PATENT SAFETY CATCHES, OR CUT-OUTS,
                                 WITH
          FUSIBLE SAFETY PLUGS AND OF ALBO METAL MICA-FOILS.

                            [Illustration]

      DIRECTIONS FOR INSERTING A SPARE MICA-FOIL.—Undo
    the Contact Screws, lift the Contact Pieces and place Foil
    fairly under, and screw down, taking care not to jam the
    Mica on to the Foil, which should be loose, so as to allow
    for expansion.

              _Certificate from the Vienna Exhibition,
                   which was protected throughout by
                      “Hedges’ Patent Fuses.”_

                        [TRANSLATION.]
      THE PATENT HEDGES’ CUT-OUTS have found a useful sphere
    of employment in the labours of the Technical Scientific
    Commission, and their construction has proved itself most
    admirably adapted to the ends in view.

         The President of the Technical Scientific Commission,
     VIENNA, _13th May, 1884_.
                                     (_Signed_) F. STEFAN.




                         W. T. GOOLDEN & CO.,

                         Electrical Engineers,

              _Contractors to Her Majesty’s Government
               and the Principal Railway Companies._

          Sole Manufacturers of the Connaught (Kapp’s Patent)
             Alternating Current Dynamo and Transformers;

             GOOLDEN-RAVENSHAW CONTINUOUS CURRENT DYNAMO;

                   Electric Motors for all purposes;

                        MEASURING INSTRUMENTS;

                           CARDEW VOLTMETERS
       (The only Reliable Instruments for Alternating Currents);
            Evershed Patent Gravity Voltmeters and Ammeters
              (Not affected by the proximity of dynamos).

     Complete Estimates furnished for Central-Stations, Plant for
     Alternating and Direct Currents, or for Batteries, Engines,
     Boilers, etc., by the Best Makers only, and of the most
                        economical types.

          ALL PLANTS SUPPLIED CAN BE TESTED AT OUR OWN WORKS.

                       _Offices and Works_:
              WOODFIELD ROAD, WESTBOURNE PARK, LONDON, W.