GILBERT
                             WEATHER BUREAU
                             (METEOROLOGY)
                                FOR BOYS


                                   BY
                           ALFRED C. GILBERT
                         Yale University, 1909


                              Published by
                       THE A. C. GILBERT COMPANY
                            NEW HAVEN, CONN.

    New York      Chicago      San Francisco     Toronto      London




                          Copyright, 1920, by
                             A. C. GILBERT
                            New Haven, Conn.




                          WEATHER INDICATIONS
                         A Study of the Weather


In the minds of most people a very silly notion prevails about the
weather and the weather man. They have a general impression that the
weather knows no laws—that it is lawless and reckless, fickle and
changeable; that the weather man is a sort of conjurer, and by some
mysterious gift he is able to prophesy things that most people know
nothing about. Nothing could be further from the truth.

After you have carried out the simple experiments described, and have
read this text, whether you have a scientific trend of mind or not, you
will at least learn that the weather is a science, like electricity,
chemistry, or medicine; that its laws are uniform, constant, and
unchanging, and there is really nothing mysterious about it. The weather
man is a scientist and by means of instruments, which indicate certain
things, he comes to definite conclusions. He is not a prophet; he does
not prophesy; he forecasts.

If you are interested in having a Weather Bureau station of your own,
you will find it one of the most interesting things you ever acquired in
your life. You will soon gain a knowledge of a subject that most people
are quite ignorant of, and if you desire to stand for leadership among
your boy friends, it may be achieved by knowing about those things that
to most boys, and in fact to adults, assume a mysterious and magical
aspect.

A Weather Bureau station at your home will give you a source of
pleasure, fun, and insight into a science that is intensely interesting,
easy to understand, fascinating and worth while knowing. The importance
of the subject cannot be overestimated. It has an influence on the whole
world; it affects our health; it affects our comfort; it means success
or failure in farming; it has an immense influence upon transportation.
When ready to move perishable goods, the transporter must have
indications of what the weather is going to be.

The weather observer is the guardian angel of the ships at sea; some men
have doubts as to whether medicine itself has saved more human lives
than the study of the weather and the practice of weather observing. It
is not unusual for those who live along the coast to see ships hovering
into cover long before a storm approaches, for the wonderful weather
bureau system operated by the United States Government gives warnings
and danger signals all over the country. Statistics show that losses
have been reduced seventy-five to eighty per cent through this system.
The marine warnings are so perfect, so prompt, and so efficient that for
a great many years no long or hard storms have ever reached any part of
the United States without advance warnings and danger signals being
shown beforehand.

When a storm is brewing, the Government’s wonderful Weather Bureau
organization watches every atmospheric change with the greatest care and
concern, and takes observations every few hours, and telegraphs the
indications to all places where a warning should be given. Thereby
perishable goods that need protection can be looked after. When extra
hazardous storms and weather changes of a severe character are
indicated, hundreds of thousands of telegrams are sent out in a
comparatively short time, to all parts of the country, so that
interested parties may prepare for such conditions. One can readily see
the great service rendered and the satisfaction it must be to the
shipper and the farmer to know that his property, which might be
destroyed by a bad storm or low temperature, is being constantly and
carefully guarded against danger. Not only storms and great cold waves
have been forecasted, but floods have been anticipated and warnings
given.

This brings us to a study of the subject “Weather,” and the best way to
learn about the weather is to first learn about the air.


                                THE AIR

If you were to ask ninety-nine people out of a hundred to take the
stopper out of a bottle, to look into it, and to smell its contents, and
then ask them if, in their opinion, it contained anything, the
invariable answer would be: “It contains nothing.”


                            EXPERIMENT NO. 1

Take the stopper out of a bottle and endeavor to pour water into it
rapidly and see what happens. (See Fig. 1.) One of the laws in Physics
is that no two bodies can occupy the same space at the same time. After
doing this experiment, you will come to the conclusion that the bottle
does contain something, and that “something” is matter, and that matter
is air. There is in the bottle probably as important a thing as you
could possibly conceive of, because even this earth without its ocean of
air would be a world of desolation; for air sustains life itself, and
when agitated, develops great strength. It may be whirled about into a
hurricane blast and assume such violent proportions that villages will
be swept away, and great waves of water will be raised, upon which ships
can be tossed about like so much chaff. We all know that air can become
so cold that great suffering will be caused, and so hot that it will
make life almost unbearable. We really live in an ocean of air.

[Illustration:

  Fig. 1
]

[Illustration:

  Fig. 2
]


                            THE OCEAN OF AIR

As the fishes live at the bottom of the ocean of water, mankind lives at
the bottom of an “ocean of air.” (See Fig. 2.) No one is absolutely
certain about the depth of this air, but it has been estimated as low as
forty miles and as high as two hundred miles. Balloons have gone up to a
height of nearly nineteen miles (100,320 feet). We do know that the
higher we go, the thinner the air becomes. It is practically impossible
for man to ascend into the air more than five or six miles, owing to the
fact that the air above that height is so thin that there is not enough
to breathe. Naturally, the air at the bottom is more compact because of
the vast amount of air above. The air is a great weight lying upon
us—14.7 pounds per square inch of surface.


             HOW TO PROVE BY EXPERIMENT THAT AIR HAS WEIGHT

The air-globe is a piece of apparatus for demonstrating that air has
weight. (See Fig. 3.) First, the air-globe is weighed and then the air
is pumped into it; its stop-cock is closed and the globe is reweighed.
It will be found to have gained in weight. This is conclusive that air
is matter and that it has weight.

[Illustration:

  Fig. 3
]

[Illustration:

  Fig. 4
]

Of great importance to us in the study is the next fact, that air exerts
pressure on everything about us and upon ourselves.


                            EXPERIMENT NO. 2

A tumbler is filled with water and a piece of paper placed over the top
of it. The glass is then inverted, holding the hand over the paper so
that none of the water will come out. On taking the hand away, although
the glass of water is inverted, the contents do not leave the glass.
(See Fig. 4.)

[Illustration:

  Fig. 5
]


                               CONCLUSION

It demonstrates that the air is exerting a pressure from below on the
paper, which is more than enough to support the weight of the water. The
tumbler may be placed in any position and yet the water will stay in.
This air pressure is exerted alike from all directions, and this
pressure, which is 14.7 pounds to the square inch, is weighed down by
the air about it and may be likened very much to ordinary water in that
it exerts pressure in all directions.


                            EXPERIMENT NO. 3

Take an ordinary rubber sucker, such as is used on the end of a dart,
and attach it to a string. Force this down on a piece of glass. (See
Fig. 5.) The glass can then by lifted by the pressure of the air that
holds the rubber to it.

We are indebted to a German experimental philosopher named Otto Von
Guericke for knowledge of atmospheric pressure. Guericke is
distinguished by his original discoveries of the properties of the air.
He was born at Magdeburg in Prussian Saxony, November 20, 1602. He
became interested at an early age in the politics of his city, and in
1627 was elected alderman, and in 1646 Mayor of Magdeburg. While serving
in the above capacities, he devoted his leisure to science, especially
on the creation of a vacuum and the action of bodies in a vacuum. His
first experiments were conducted with a pump on a barrel of water. After
drawing off all the water, he still found that air permeated the wood of
the barrel, so he substituted a globe of copper and pumped out air also.
He thus became the inventor of the air pump and illustrated in a simple
but effective way the force of atmospheric pressure.

[Illustration:

  Fig. 6
]

By placing two hollow hemispheres of copper (see Fig. 6) together, and
exhausting the air, he found that fifteen horses pulling one way and
fifteen pulling the opposite were unable to pull the hemispheres apart.

He further demonstrated that in a vacuum all bodies fall equally fast,
that animals cannot exist therein, or, in fact, living matter. He is
also credited with being the inventor of the air balance and a type of
weather cock, called the anemoscope. He was interested also in
astronomy.

[Illustration:

  Fig. 7
]


                            EXPERIMENT NO. 4

This experiment should interest you very much, because it is going to
lead up to the subject of weather instruments, and is absolutely
essential that you understand the fundamental principles in order to
intelligently interpret these instruments. This experiment will explain
one of the principles of the barometer.

Take a glass tube thirty-two inches long and one-quarter or one-eighth
inch in diameter, and fill it with mercury, care being used to get rid
of all the air bubbles. The mercury should be poured in with an eye
dropper, one end of the tube being sealed, until filled, and then the
finger is placed over the open end. (See Fig. 7A). The tube is inverted
and immersed in a reservoir of mercury and clamped to an upright stand.
Immediately the mercury falls to about thirty inches. (See Fig. 7B). Ask
yourself what held the mercury up in the tube. Again the answer is that
the pressure of the air on the mercury in the reservoir causes it to
rise and fall in the tube, as the pressure of the air changes. You will
soon learn what causes these changes in the pressure of the air.

[Illustration:

  Fig. 8
]


                            EXPERIMENT NO. 5

Have you ever asked yourself why it is that the wind blows? Why doesn’t
it stand still?

Put your hand over a lamp chimney under which the lamp is lighted. You
will soon discover that the heat is rising. Four things in connection
with this are of great importance:

  1. Air has weight.

  2. When heated, it rises.

  3. Air expands when heated.

  4. Warm air will gather and hold more moisture than cold air.


                            EXPERIMENT NO. 6

Cut a piece of stiff cardboard in a spiral shape. Thread a piece of
thread through a pinhole in the center point of the spiral and fasten
this to a support so that it swings freely in the air. (See Fig. 8.)
Under this put a little alcohol lamp, or put it over a gas jet or
radiator.


                              WHAT HAPPENS

The cardboard will spin around rapidly. Ask yourself what causes this.
It is the force of the hot air rising which caused the spiral cardboard
to turn in such an attractive manner.


                            EXPERIMENT NO. 7

[Illustration:

  Fig. 9
]

When you are in a warm room, find out which air is the hottest, that in
the upper or that in the lower part of the room. This answer you can get
by placing the thermometer low down in the room and then putting it up
near the ceiling. This is another conclusive proof that hot air rises.

Another experiment that is quite familiar to all of us is that of
opening the windows of a heated room a few inches top and bottom, and
holding a lighted match or smoke paper at the bottom, when you will find
that it blows the flame or smoke inward. Then put it near the top of the
window and it will be drawn out. The same answer is true; the cold air
is rushing in from below to take the place of the hot air rising and
going out at the top. (See Fig. 9.)

[Illustration:

  Fig. 10
]


                            EXPERIMENT NO. 8

This experiment is even more important than the preceding one, and you
should by all means do it, for it is going to prove more conclusively
than anything else what causes the wind, and in miniature it is a real
storm.

Place a little alcohol lamp on the table, or a wax candle will do. Over
this place an ordinary lamp chimney, lifting it a short distance off the
table, and it can be held in position by any little object. (See Fig.
10.) Over the chimney hold some smoke paper. (Smoke paper is nothing
more than filter paper, or brown wrapping paper of a soft texture.) From
the experiments already visualized to you, you should know what to
expect. You will again see that the heated air is rising; it has
expanded and become light. Now what becomes of the air that is rising
and where does it go? In doing this experiment be careful not to make
any unnatural movements that will change the current of wind. Stand
perfectly still so that the experiment will be perfect, because you are
now producing in miniature a real storm, or demonstrating the cause of
wind.

The next observation—what happens at the bottom of the chimney? Here you
will find the outside air is coming in, the same as it did in the window
experiment. Particularly, notice however, that the smoke enters
underneath the chimney from all directions, and the smoke paper should
be moved away from the glass chimney to determine the distance at which
the smoke flames will still be drawn into the chimney.

You now produced for yourself in miniature a storm and wind. The air
that has been heated rises over a heated area, and cooler air from all
directions around is passing into the space underneath the chimney and
taking the place of the heated air that has gone up. This experiment
illustrates what takes place, except on a smaller scale, out in the
atmosphere when a portion of the earth becomes heated. If this is clear
to you, it will help you to understand the main principles underlying
storms and winds, which will be given later on.


                            EXPERIMENT NO. 9

Equally important is the last part of the experiment, which consists in
lifting the lamp chimney off the table altogether and continuing with
the smoke paper. Note results that you get now. The smoke will spread
out over a large area.


                          WHAT IS THE WEATHER?

By the weather we mean the temperature, the amount of moisture in the
air, the pressure of the air, the movement of the air, and all the
conditions that have to do with the atmosphere, such as heat, cold,
rain, snow, sleet, fog, frost, dew, etc. It has to do with everything,
from calmness and clearness to cloudiness and blizzards.


                         THE EFFECT OF THE SUN

The sun has a great deal to do with the regulation of the weather. Its
heat causes evaporation; it is the rays of the sun that raises the vapor
from the water and brings it into the air; it is the cooling of this
vapor that produces the rain, hail and sleet storms, and its brilliancy
causes a difference in air pressure at times. It is this difference in
air pressure that produces winds, as you will learn later.


                                HUMIDITY

The state of the air with respect to the vapor that it contains is
called its humidity. The humidity is said to be high when the air is
damp, and low when the air is dry. Humidity and moisture in the air are
important factors about the weather. It is lack of humidity that has
more to do with poor health, colds, and catarrh than anything else. The
importance of proper humidity in houses and buildings cannot be
emphasized too greatly. Proper humidity will save twelve and one-half
per cent in the cost of heating. The great majority of people are under
the impression that colds are caused by sudden change in temperature,
but the most colds are actually caused by stuffy, hot rooms. The reason
that some people complain that 70° is not hot enough is because the
humidity is too low, but if the moisture is brought into the air at a
proper degree, the humidity is maintained. You will find that 68° will
be a proper temperature to maintain in a room. The reason for this is
that the air in the room is dry and the heat actually goes through it.
In other words, it does not warm it; moist air stops radiation.
Consequently, the result is that it warms it. In other words, moisture
is nothing more than clothing, and this accounts for the fact that in a
hot room, where there is no moisture, we heat our rooms beyond the
degree that is necessary in order to feel any reasonable amount of
comfort. Dry air allows too much radiation from the body and too rapid
evaporation, which makes us cold.

The following experiment illustrates the above statement. Place a few
drops of water on a smooth surface, such as a table top or ordinary
board, and over this a watch glass, containing a small quantity of
ether. In order to hasten evaporation, blow a current of air across it,
and it will be found that the glass will be frozen to the board. This is
caused by the evaporation of the ether, which uses up heat.

You know a great many times when you go out into the wind how cold it
feels, and yet if the wind would actually stop, you would think it warm.
It is the wind that causes the rapid evaporation and makes the surface
of the skin feel cold. As it is true that the moisture in the air acts
as a blanket to us in our homes, it is likewise as true that the vapor
in its natural form outside of the house acts as a blanket for the
earth. Do you realize that without this blanket we would burn up in the
summer and freeze to death in the winter?


                                  FOGS

Water vapor in the air is transparent, but when this water vapor becomes
cooled, a portion of it becomes precipitated, which is no more or less
than drops of water that are extremely small, but yet large enough to
become transparent, and the atmosphere in this state is called fog. In
reality, fogs are nothing more than clouds near the surface of the
earth. When the ground is at a higher temperature than the air, it
produces fogs. They are also produced when a current of moist air and a
current of hot air pass over a body of water at a lower temperature.
Consequently, you can easily see that fog will never form when it is
dry.


                                  HAIL

After rain drops have been formed and they freeze in their passage
through the air, they then become hailstones.


                                  SNOW

When condensation of vapor in the air takes place at a temperature below
32° F., a deposit is made in a solid condition, either in the form of
snow or hail. Snow is made up of crystals, most of which have great
beauty. Everyone should observe either by the naked eye or by a
magnifying glass the little crystals caught before they are broken. When
you see extremely large snowflakes in the sky, you can be sure the
temperature is very near freezing, for at this point the flakes are more
or less damp and the snow is heavy and wet. Now if there is a slight
wind, the crystals become broken and separate flakes unite to form large
masses of snow. Generally speaking, ten inches of snow makes one inch of
rain.


                                  DEW

If the temperature of the ground falls below the dew point of the air,
the air deposits on the cooler surface moisture in the form of small
drops of water, which we call dew drops. Where the temperature of the
ground becomes cooler than the air above it, a rapid cooling by
radiation on a clear night has taken place; and if the dew point or
frost point has been reached by the ground, the air just above the point
is several degrees warmer.


                                 FROST

When the moisture in the air that is in contact with the earth is
condensed above the freezing point, dew is formed. When below the
freezing point, frost is formed or deposited on the earth. It is readily
understood from this that the surface on which the frost is deposited is
at a freezing temperature, while the air above it may not be freezing.
Naturally, you can expect frost when the temperature falls to a point 8°
or 10° above the freezing point. Clear, calm nights are favorable for
frost, because the absence of clouds helps radiation, that is, it draws
heat away from the earth. If there are clouds, it prevents this
radiation.


                         THUNDER AND LIGHTNING

Free electricity is always in the air. During clear weather it is
generally positive; during cloudy weather it is negative. This
electricity is carried in the air by the moisture. As dry air is a
non-conductor of electricity, in fair weather the electrified particles
of air are insulated and therefore acquire very little intensity. The
clouds having been formed and being filled with moisture, form an
excellent conductor of electricity, which acquires considerable
intensity. It is a well-known physical law that two bodies having
opposite electricities attract each other, and those having like charges
repel each other. From this, two clouds having opposite charges rush
together and produce the phenomena, called lightning, which is
accompanied by an explosion called thunder. Often we see several flashes
of lightning and then hear several thunder crashes, which is caused by
only one section of a cloud discharging its electricity at a time.

As a cloud attracts the opposite charge of electricity from the surface
of the earth beneath it by inductive influence, often we see a discharge
of electricity from the cloud to the earth, the charge usually being
received by such objects as hills, trees, church spires, high buildings,
etc. Bodies containing large quantities of moisture are susceptible to
strokes of lightning, as the moisture causes them to become good
conductors of electricity. Also trees on the outer edge of a forest are
more liable to be struck than those farther in.

There are several forms of lightning, such as zigzag, ball, sheet, and
heat lightning.

Zigzag lightning, as the name implies, follows an irregular course,
producing a long zigzag line of light, sometimes ten miles in length,
and is caused by the air producing a field of resistance to the path of
electricity, causing it to seek a path of less resistance.

Ball lightning appears like a large ball of fire, usually accompanied by
a terrific explosion. This is the result of the bodies being charged
with electricity of great intensity, and travels in a straight path, as
it has enough strength to oppose any resistance placed in its path.

Heat lightning is usually seen on warm evenings, especially during the
summer, and very often unaccompanied by thunder, due to the great
distance of the lightning clouds from where we are located, thus
diminishing the intensity of the thunder. The electricity of the clouds
escape in flashes so feeble as to produce no audible sound.

Sheet lightning is a diffused glare of light sometimes illuminating only
the edges of a cloud, and again spreading over its entire surface.

Ordinary flashes of lightning last but the minutest part of a second.

Thunder is the re-entrance of air into an empty space. The vacuum is
created by the lightning in its passage through the air. The violence of
thunder varies according to the intensity of the electrical flashes.

Because of the fact that light is transmitted almost instantaneously,
while sound travels at a speed of eleven hundred feet per second, the
sound will not reach the ear for some few seconds after the flash of
lightning. Average space of time between a flash and a report is about
twelve seconds. The longest interval is seventy-two seconds and the
shortest one second. Prolonged peals of thunder are, in some cases, due
to the effect of echoes. These peals are especially noticeable in
mountainous countries. The echoes are also produced by the reflection of
sound from the clouds.

Thunder storms are distributed over certain sections of the globe,
occurring most frequently in the equatorial regions and diminishing as
we approach the polar regions. Within the tropics, where there are trade
winds, thunder storms are rare. Thunder storms are common in warm
climates because evaporation supplies electricity in great abundance,
and thus precipitation of the air is brought about.

[Illustration:

  Fig. 11
]


                               TORNADOES

Tornadoes are caused by the air becoming abnormally heated over certain
areas. Likewise, caused by a difference in pressure. Tornadoes are local
whirlwinds of great energy, generally formed within thunder storms. They
are most easily distinguished by a funnel-shaped cloud that hangs from
the bottom of the larger thunder cloud mass above it. The funnel is
formed around a violent ascending mass of whirling winds; its diameter
sometimes reaching several hundred feet, being larger above than below,
the winds themselves covering a greater space.

[Illustration:

  Fig. 12
]

The whirling funnel advances generally to the east or northeast at a
rate of twenty to forty miles an hour, accompanied by a deafening noise,
destroying everything in its path. The path is usually less than a
quarter of a mile in width.

The winds in the vortex (the apparent cavity or vacuum formed in the
center of the whirling winds) of the tornado attain an incredible
violence, and due to this fact houses are shattered, trees uprooted, and
human lives lost, besides other devastation of property and animal life.
It is, therefore, the vorticular whirl that causes the destruction
produced by tornadoes.

Tornadoes are more frequent in the southern states than anywhere else in
the country, and occur in the warmer months.

The velocity of the whirling winds in a tornado increase towards the
center, and it is because of this that the point of danger is only a
small distance from the funnel cloud. The direction of the whirling
motion is from right to left. From the appearance of the funnel formed
in a tornado, it looks as though the currents were descending from the
cloud to the earth, when in reality the currents are ascending. The
ascending current draws on the warm and moist air near the surface of
the earth for its supply, and this inrush of air in a spiral form into
the low pressure core made by the higher whirl constitutes the
destructive blast of the tornado.

Tornadoes approach rapidly, and it is therefore almost impossible for
those who happen to be in their path to escape their violence.

A tornado at sea is termed a water spout.


                                RAINFALL

You will recall a preceding statement that evaporated humidity turns
into water when it becomes cool below a certain point. (See page 14,
Effect of the Sun.) A given amount of air will hold a certain amount of
moisture. For example, let us assume that a cubic foot of air (see Fig.
11) is saturated, that is, it is holding all the water it will retain.
Now if this cubic foot of air is cooled, it will contract, and as a
result there will not be enough room to hold both the air and moisture,
so the excess moisture will leak out. (See Fig. 12.) The result of this
reduction in temperature causes precipitation, simply because the air
cannot sustain the water that is in it. Therefor, at any time when
moisture in the air has reached the point of saturation and a chilling
takes place, due to the air becoming cold, rain follows. This may happen
as a result of air rising into higher places or cooler levels, or
through its contact with cooler surfaces.


       WHY WE GET SUCH HEAVY RAINFALLS SOMETIMES AROUND MOUNTAINS

The air becomes thoroughly saturated. When air is comparatively warm, it
will expand, and this air, which is heavily saturated is brought up by
breezes onto the mountain range, which is cold, causing the air to lose
its heat and contract and really force the water out of the air. The
same principle applies to sea breezes bringing rain.


                                 WINDS

Winds are caused as a result of differences in temperature between the
various layers of the atmosphere. A certain amount of air becomes heated
and rises, and as explained before, expands. As the air expands, it
becomes lighter, and because it is light it goes upward toward higher
regions. It also flows from hot to cold countries. A good illustration
of this is the sea breezes. If you have lived around the seashore in the
summer time, you will have observed that during the hot part of the day
the winds generally blow from the sea toward the land. At night the
direction of the wind is reversed, that is, it blows from the land to
the sea. Why? Because the land during the day retains its heat, while
the water diffuses it. What is the result? The air on the land expands,
becomes light. The air over the water being cool, it does not expand,
and the result is that it presses toward the land. At night the land
loses its heat more rapidly than the water, so that it is not long
before the land is cooler than the water, and when this happens, the air
over the land, which has become cooler, presses seaward.


                             KINDS OF WINDS

=Mountain Breezes=: Caused by the heating and cooling of the hills and
valleys.

=Avalanche Winds=: Winds that are in front of a landslide, caused by the
movement of the snow forcing the air in front of it.

[Illustration:

  Fig. 13
]

[Illustration:

  Fig. 14
]

[Illustration:

  Fig. 15
]

[Illustration:

  Fig. 16
]

[Illustration:

  Fig. 17
]

=Volcanic Winds=: Due to volcanic eruption, which produces an outrush of
air.

=A Squall=: Due to the sudden disturbance in temperature.

=A Simoon=: A desert wind.


                            VELOCITY OF WIND

The wind blows a great deal harder on water than on land, because on
land it meets with various obstacles, whereas it has very little
friction on the water.


                         THE FORCE OF THE WINDS

       Wind blowing at 20 miles per hour has a force of  1¼ lbs.
       Wind blowing at 35 miles per hour has a force of  6 lbs.
       Wind blowing at 50 miles per hour has a force of 13 lbs.
       Wind blowing at 75 miles per hour has a force of 28 lbs.
       Wind blowing at 90 miles per hour has a force of 40 lbs.


                              DAY SIGNALS

[Illustration:

  Fig. 18
]

[Illustration:

  Fig. 19
]

[Illustration:

  Fig. 20
]

[Illustration:

  Fig. 21
]

[Illustration:

  Fig. 22
]

[Illustration:

  Fig. 23
]


                             NIGHT SIGNALS

[Illustration:

  Fig. 19A
]

[Illustration:

  Fig. 20A
]

[Illustration:

  Fig. 21A
]

[Illustration:

  Fig. 22A
]

[Illustration:

  Fig. 23A
]


                             NAME OF WINDS

Beaufort’s scale, used in preparation of all Weather Bureau wind
forecasts and storm warnings.

        FORCE        DESIGNATION            MILES PER HOUR
            0 Calm                           From       0 to  3
            1 Light Air                      Over       3 to  8
            2 Light breeze (or wind)          „         8 „  13
            3 Gentle breeze (or wind)         „        13 „  18
            4 Moderate breeze (or wind)       „        18 „  23
            5 Fresh breeze (or wind)          „        23 „  28
            6 Strong breeze (or wind)         „        28 „  34
            7 Moderate gale                   „        34 „  40
            8 Fresh gale                      „        40 „  48
            9 Strong gale                     „        48 „  56
           10 Whole gale                      „        56 „  65
           11 Storm                           „        65 „  75
           12 Hurricane                       „        75

The following method of transmitting weather signals by means of flags
was used for a number of years, but the newspapers now convey the same
news to the interested public:

1. A square white flag indicates fair weather. (See Fig. 13.)

2. A square blue flag indicates rain or snow. (See Fig. 14.)

3. A white and blue flag, half white and half blue, indicates local rain
or snow. (See Fig. 15.)

4. Black triangular flag indicates a change in temperature. (See Fig.
16.)

5. White flag with a square black center indicates cold wave. (See Fig.
17.)

When No. 4 is placed above No. 1, 2, or 3, it indicates warmer weather;
when below, colder; when not displayed the temperature is expected to
remain stationary.

The following flag warnings are used along the Atlantic and Gulf coasts
to notify inhabitants of this section of the country of impending
danger.

=Fig. 18. The Small Craft Warning.= A red pennant indicates that
moderately strong winds that will interfere with the safe operation of
small craft are expected. No night display of small craft warnings is
made.

=Fig. 19. The Northeast Storm Warning.= A red pennant above a square red
flag with black center displayed by day, or two red lanterns, one above
the other, displayed by night (Fig. 19A), indicates the approach of a
storm of marked violence, with winds beginning from the northeast.

=Fig. 20. The Southeast Storm Warning.= A red pennant below a square red
flag with black center displayed by day, or one red lantern displayed by
night (Fig. 20A), indicates the approach of a storm of marked violence
with winds beginning from the southeast.

=Fig. 21. The Southwest Storm Warning.= A white pennant below a square
red flag with black center displayed by day, or a white lantern below a
red lantern displayed by night (Fig. 21A), indicates the approach of a
storm of marked violence, with winds beginning from the southwest.

[Illustration:

  Fig. 24
]

=Fig. 22. The Northwest Storm Warning.= A white pennant above a square
red flag with black center displayed by day, or a white lantern above a
red lantern displayed by night (Fig. 22A), indicates the approach of a
storm of marked violence, with winds beginning from the northwest.

=Fig. 23. Hurricane, or Whole Gale Warning.= Two square flags, red with
black centers, one above the other, displayed by day, or two red
lanterns, with a white lantern between, displayed by night (Fig. 23),
indicate the approach of a tropical hurricane, or of one of the
extremely severe and dangerous storms which occasionally move across the
Great Lakes and Atlantic Coast.

[Illustration:

  Fig. 25
]

We have installed at our manufacturing plant a high-class weather
station, with equipment of the latest United States Weather Bureau
standard pattern, and are able to send out weather signals by wireless
from our own wireless station twice daily, at 4 P. M. and 7 P. M., to
all boys owning a wireless outfit. The indications are taken from our
own instruments. A description of these instruments and the method of
recording the indications will give you an insight into how the various
government weather stations arrive at their forecasts.

[Illustration:

  Fig. 26
]

On the roof of the factory is a weather vane (Fig. 34) twenty feet high,
which is connected electrically with a register in our weather office.
The register is of the quadruple type (Fig. 45), and is capable of
recording wind direction, wind velocity, rainfall, and sunshine on the
same form or sheet. Thus, we know the wind direction and can deduce
certain things relating to the weather. Mounted on the wind vane support
is an anemometer (Fig. 36), an instrument for measuring the velocity of
the wind. A rain gauge (Fig. 49) on the roof catches the precipitation,
and for every one hundredth of an inch of rainfall, a small tipping
bucket empties its contents into a receiver and a record is made on the
form in the quadruple register.

The same pen that records the rainfall also records the number of hours
of sunshine during a day, for it is not a common thing to have rain and
sunshine at the same time.

A hygrothermograph (Fig. 43) records on a form the temperature and
amount of humidity in the atmosphere.

A barograph (Fig. 44) records the pressure of the atmosphere. For
determining the pressure, we also have a mercurial and aneroid
barometer, which will be described later on.

You can readily see that it is a simple matter to obtain the weather
indications.

[Illustration:

  Fig. 27
]


                                 CLOUDS

The numberless kinds of clouds makes it quite difficult to describe and
arrange them or illustrate them in any manner that makes it easy to
recognize them. Although some may be recognized from description and
with a fair amount of observation, you will be able to classify them in
their proper place. For instance, the thunder clouds most anyone
recognizes without any experience whatever.

[Illustration:

  Fig. 28
]

There are really four simple cloud formations and three compound
formations:

=1. The Cirrus Cloud.= (Fig. 24.)

The Cirrus cloud is always seen high in the sky and at a great
elevation. Its formation is fibrous and it is particularly characterized
for its many varieties of shapes. It also has a marked delicacy of
substance and it is pure white.

=2. The Cumulus Cloud.= (Fig. 25.)

The Cumulus cloud is of moderately low elevation. It is a typical cloud
of a summer day. It may be recognized by little heaps or bushes rising
from a horizontal base. In summer-time we are all familiar with the
cumulus clouds rising with the currents of air in huge masses. They form
one of the most accurate indications of fair weather when you see them
gradually dissolving. Sometimes these clouds become very large, and,
while the texture is generally of a woolly white, naturally, when they
assume such large sizes, they gradually change in color to a darkish
tint.

=3. The Stratus Cloud.= (Fig. 26.)

This is the opposite of the Cirrus cloud, because it hangs the lowest of
all, in gray masses or sheets, with a poorly-defined outline.

=4. The Nimbus Cloud.= (Fig. 27.)

Any cloud can be classed as a nimbus cloud from which rain or snow is
falling.

Of the Compound Clouds we have:

[Illustration:

  Fig. 29
]

1. The Cirro-Cumulus Cloud (Fig. 28), which has all the characteristics
of both the Cirrus and the Cumulus. The most characteristic form of this
cloud, and the one most commonly known, is when these clouds form small
round masses, which appear to be cirrus bands broken up and curled up.
This is what people call the “mackerel” sky.

2. The Cirro-Stratus Cloud (Fig. 29), which is known when the clouds
arrange themselves in thin horizontal layers at a great elevation.

[Illustration:

  Fig. 30
]

3. The Cumulo-Stratus (Fig. 30) is the cumulus and the stratus blended
together. Their most remarkable form is in connection with approaching
thunder storms, and are often called thunder heads. They rapidly change
their outline and present a beautiful spectacle in the sky at times.

The Cirrus, Cirro-Cumulus and Cirro-Stratus are known as the upper
clouds and the others are known as the lower.


                        ATMOSPHERIC DISTURBANCES

Disturbances of the atmosphere are classified as follows: Cyclonic, or
low area storms, or anti-cyclonic, or high area storms.

[Illustration:

  Fig. 31
]

The word “cyclone” to most people immediately means a terrific storm,
whereas in weather observing the cyclonic storm is not really a cyclone
or hurricane at all. It is a storm with an atmospheric pressure below
average. Particularly important is the wind that blows about this area,
which is always spirally inward, due to the rotation of the earth on its
axis. This is probably why it is given the name of cyclonic storm, for
it bears one of the important characteristics of a real cyclone. As the
wind is deflected and moves into the storm center, it turns to the right
and in the form of a whirlwind, spirally, moves around the storm center.
(See Fig 31.) It is this whirling process that has given it the name,
cyclonic storm.

As the air rises over the point of low storm area, or, in other words,
the area of low pressure, and travels into the atmosphere, it is not
permitted to rise to any great height, because it is always acted upon
by the force of gravity and is being pulled back to earth again. We
assume that because of this fact, this rising air which has been pulled
back to the earth again piles up in certain places, causing the
barometer to rise. Such a center as this is known as a high barometric
center or the anti-cyclonic area. Here the circulation of the air is
exactly opposite to that of the cyclonic area.

[Illustration:

  Fig. 32
]

We are all more or less acquainted with these anti-cyclonic storms,
because in winter these great masses of air rise up from the warm areas,
pile up, and form high pressure areas over the mountains of Canada, and
soon this high pressure works down upon us as blizzards and cold waves.

We have described quite minutely the movement of the wind about these
points of high pressure and low pressure and have shown you the map and
have illustrated the high pressure and low pressure areas, but there is
still another feature that is of great importance to us, and that is the
movement of the storms and the fact that storms have a progressive
movement from west to east.

These storms move more rapidly in the United States than elsewhere, and
are more rapid in their movement in winter than in summer. Their speed
is almost one half again as great. The average velocity of the low area
storm in the United States is about twenty-five miles an hour in June,
July, August, and September, and from October on they continue to
increase.


                              LOW PRESSURE

We can summarize low pressure storms generally in the following manner:
They have a wind circulation inward and upward and are elliptical in
form. Their velocity varies from six hundred to nine hundred miles per
day, moving in the same general direction. They are characterized in
their eastern quadrants by cloudy weather, southerly and easterly winds,
precipitation, temperature oppressive in summer and abnormally high in
winter, falling barometer, increasing humidity and followed by clear
weather, rising barometer, decreasing humidity and falling temperature
in the western quadrants.

Buys Ballot’s law of winds is, that in the Northern Hemisphere if one
stands with his back to the wind, the low barometric pressure will be
invariably to the left hand; in the Southern Hemisphere the lowest
pressure is always to the right. This law explains one of the
characteristics of low pressure storms.


                         AREAS OF HIGH PRESSURE

In speaking of low pressure storms we called them storm centers, because
nearly always they are of sufficient intensity to bear that name, but in
high pressure areas we do not speak of them as storm centers.

The Buys Ballot’s law applies to anti-cyclonic as well as cyclonic
storms, that is, when one’s back is to the wind, the lowest barometric
pressure is at the left and the highest at the right. This is probably
understood by saying that in the cyclonic storms, the winds blow inward,
contrary to the hands of a watch, and in the anti-cyclonic they blow
outward, that is, in the same direction to the direction of the hands of
the watch.

In the United States, the cyclonic storms are not as frequent as low
pressure storms, and it is safe to say that probably not more than
one-third of the entire anti-cyclonic areas can be classed as storm
areas.


                             WHY AIR RISES

Another very interesting experiment is to secure a long-stemmed glass
bulb (see Fig. 32). Arrange this apparatus as illustrated, with the stem
of the bulb immersed in the water. The glass bulb condenses the air.
When you first put it into the water nothing happens, but as soon as you
apply heat the air bubbles come out of the end of the tube. This means
that the air in the tube has expanded and part of it has come out
through the stem of the tube and the remainder is lighter. It is well to
remember, when air is heated it expands and becomes lighter. This fact
is extremely important to remember, because it has a great deal to do
with the important instrument, the barometer, which is used to measure
the pressure of the atmosphere and is an important element in the
question of humidity, as you will learn later. By this time you no doubt
have learned that:

1. Air has weight.

2. Heated air expands, becomes lighter, and exerts less pressure.

3. Cold air comes from the side to take the place of hot air that rises.

When the rays of the sun heat an area of the earth, the air over such a
place expands and becomes lighter, naturally rising, and the result of
this is that the winds are produced by cool air moving in to take the
place of the heated air. This cool air moves in from all directions.
When such a thing happens at any point on the earth’s surface, it is
known as a storm center, an area of low pressure.


                       WHAT IS A CYCLONIC STORM?

Because of the rotation of the earth on its axis, a force arises which
tends to deflect to the right all motions in the northern hemisphere,
and to the left all motions in the southern hemisphere. The winds
flowing toward the storm center are turned to the right or left and move
in a spiral around the storm center. This system of whirling winds
around a central region of low pressure produce what is termed a
cyclonic storm. Storms have a tendency to move in an easterly or
northeasterly direction, and at a rate of from five hundred to seven
hundred miles a day. Cyclonic storms, although we look upon them as
being very severe, are very often mild and not of an intensive
character.


              WHICH WAY DOES THE WIND BLOW AFTER A STORM?

From the descriptions and experiments preceding, which illustrate the
development of storms, reference was made only to the winds blowing in
toward the storm center. Naturally the question comes to your mind: What
happens to them after the cold air has taken the place of the warm air?
They change to other directions when the storm has passed away. It is
because of this fact that we look for a change in weather conditions
when the wind changes—a very important sign that you will be interested
in later on.

It is well to mention here a thing that is going to be very important to
us when we study the barometer, that is, the pressure of the atmosphere.
Should the pressure of the air, which is normally at sea level 14.7
pounds to the square inch, change, that is, become lighter, it would not
exert so much pressure on the column of mercury in the tube of the
barometer and the mercury would drop in the tube. (See Fig. 7.) On the
other hand, if the weight of the air was increased, that is, if it
became heavier, it would force the mercury to rise in the tube. This
should be quite clear to you, because it is the lightness and heaviness
of the air that is going to interest us more particularly than any other
part of the subject when we get into the study of the atmospheric
changes, what causes them, and the indications that lead up to our
conclusions. In order that this principle is absolutely clear to you,
you should perform Experiment 4, or if you have not facilities for doing
it, it is well to see it performed in any physics laboratory.

Immediately you ask yourself: If air has such a tremendous pressure as
14.7 pounds to the square inch, why is it that a weight of air amounting
to thirty-five thousand pounds bearing down on the average individual
does not cave the body in? Simply because air penetrates the body so
easily that it exerts as much pressure on the inside as on the outside,
and thereby equalizes itself. For instance, if you go down into a subway
or a caisson (a water-tight box or chamber within which submarine
construction is carried on under great air pressure to keep out the
water), where the pressure is sometimes greater than it is outside, have
you noticed the effect this pressure exerts on the ear drums? As it
becomes greater, you may equalize it by swallowing, which allows the air
to get back of the ear drums through the Eustachian tubes, which lead
from the mouth to the inner ear.


                                MOISTURE

Water vapor is always present in the air.


                           EXPERIMENT NO. 10

Expose a piece of dry potash to the air. You will soon discover that the
potash will dissolve. It has taken up water from the air.


                           EXPERIMENT NO. 11

Put a piece of ice in a pitcher of water and allow it to stand in a warm
room. You will soon notice that little beads of perspiration collect on
the outside of the pitcher. This moisture is air being condensed.

Water vapor is part of the atmosphere. Some of it is always present in
the air. The amount of vapor that the air can hold depends upon the
temperature. When the temperature is warm, the air will hold more water.
For instance, at 100° F. a cubic foot of air will hold 19.79 grains of
vapor; at 80° F., 10.95 grains; at 50° F., 4.09 grains, and 32° F., 2.17
grains. At 32° F. is the freezing point on the Fahrenheit scale.

Air containing as much water vapor as it can hold is saturated. If the
air is suddenly cooled down, that is, if the temperature falls when the
air is saturated, air molecules are contracted, and it must give up the
water, which produces rain. The ocean and the Great Lakes are the source
from which the air gets its water. It rises into the air in the form of
vapor, that is, vapor rising from the surface of the water, and the wind
distributes it over the land. Condensation turns it into clouds, and
when it is over-saturated, or rather, when the temperature drops and the
air is unable to retain any more water, then it forms into drops of
water and falls as rain. When the clouds get into the air, below the
freezing point of the water, the drops of water are changed into ice
crystals or snow flakes.

When the ice crystals are just at the point of melting into water, due
to the rise in temperature, the snowflakes lose their form and the
result is sleet.


                      HOW CAN WE USE THESE FACTS?

So far we have described, in a general way, certain facts about the
elements of the air, such as temperature, pressure, humidity,
precipitation, evaporation, clouds, winds, etc., and these facts of the
elements enter into a very interesting phase of weather observation
which we will designate as prophesying without instruments or
forecasting by physical science. When we come to the more interesting
and scientific part of weather observation, we will drop the word
“prophecy,” because the instruments that are used to measure these
elements are going to indicate certain things to us that will lead you
to more definite conclusions. Hence, the following observations are what
have given an opportunity to the weather prophet or to those people who
have been credited with some mysterious power to prophesy what the
weather is going to be. They are not definite or conclusive, and they
cannot always be depended upon, but they certainly are significant and
interesting, and a description of weather would not be complete without
a list in chronological order of a series of phenomena or physical signs
of this character that have lead certain men to gain quite a reputation
for prophesying what the weather is going to be.

[Illustration:

  Fig. 33
]


                              APPEARANCES

Various appearances that come in the sky.

For instance, a good example is in the case of the thunder storm, which
can be determined at least a few hours in advance, by the movement of
the clouds and the forms they take. In every locality there is a
direction that clouds take that forecasts bad weather, and there is a
direction that clouds take that forecasts fair weather.

When you see a halo about the top of a mountain, you know that bad
weather is expected. The same is true when a halo appears about the
moon. This indicates rain, or if the lower clouds break up and the upper
clouds, or a second light covering of clouds, are seen above the lower
ones, it speaks for continued bad weather. In some localities if rainy
weather is continuing for some time, and a certain change in wind sets
in, it will indicate that good weather is coming.

These observations will be readily understood as being adapted for
certain localities and are not general. It is always necessary that the
observer adapt himself to these localities and study them, so that he
can make prophecies accordingly. It should be borne in mind that these
prophecies are only possible from one day to another.


                        WHAT THE CLOUDS INDICATE

When high clouds are seen crossing the sun or the moon in a different
direction from the lower clouds, this indicates change of wind toward
the direction of the higher clouds. When you see hard-edged clouds, look
for wind. When you see delicate soft clouds, look for fine weather and
probably moderate breeze or high breeze. When you see gloomy dark clouds
in a blue sky, look for slight winds. When you see a bright blue sky
through fine clouds that are soft and delicate, this indicates fine
weather. When you see soft-looking clouds, you can expect less wind, but
probably rain. But when the clouds become hard and ragged, tufted and
rolling in appearance, stronger winds are coming. When you see small
clouds that are inky looking, look for rain. When you see light clouds
traveling across heavy hard masses of clouds, this indicates both wind
and rain, but if the light scud clouds are alone, you may expect wind
only. Misty clouds forming or hanging over the peaks of hills indicate
both wind and rain. If during a rainy spell they ascend or disperse the
weather is pretty certain to clear up. If there has been fine weather
and you begin to see light streaks in the sky which are distant clouds,
and they continue to increase and grow into cloudiness, this indicates
rain.


                        SUNSET AS AN INDICATION

When the sun is setting and the sky in the west presents a color of
whitish yellow or radiates out at a great height, rain can be looked for
during the next night or day. Gaudy colors where clouds are definitely
outlined indicate probably wind and rain.

Before setting, if the sun looks diffused and the color is a brilliant
white, this forecasts storms. When the sun sets in a slightly purple sky
and the color at the zenith is a bright blue, this indicates fine
weather. A red sunset generally indicates good weather, whereas a ruddy
or misty sunset indicates bad weather.


                         WHAT THE SKY INDICATES

When you see a dark, dismal sky, look for rain. A sky with a greenish
hue, described as a sickly-looking sky, is an indication of both rain
and wind. A sailor’s sky, which is red in the morning, means either wind
or rain, and it makes no difference if the sky is cloudy or clear, if at
sunset it is rosy, it indicates fine weather. A gray sky in the morning
indicates fine weather. When daylight is first seen above a bank of
clouds, look for a good stiff wind. Wind is indicated if we have a
bright yellow sky in the morning, and rain is indicated if the sky takes
on a pale yellow hue. If the sky turns bright yellow late in the
afternoon, it generally indicates that rain is near at hand. Unusual
colorations, particularly of deep intense color, indicate wind or rain.

The following appearances indicate a change in the weather: When the
atmosphere is clear and crystalline and the stars appear extremely
bright; when the background of the horizon seems to be pinned up against
the foreground; when the clouds form into delicate white film-like mist
way up overhead. (Fig. 33.)


                       WHAT FOG AND DEW INDICATE

Locality has considerable to do with what the fog indicates. As a rule,
where you have fog, there is not much wind, and as a result it does not
indicate stormy weather, unless the fog becomes heavy with overhanging
sky, then it is apt to turn into rain, but a heavy fog with a light sky
indicates fine weather. A fog in the morning generally indicates a fair
day. A rising fog is a good indication for fair weather.

[Illustration:

  _Courtesy Julien Friez & Sons, Baltimore, Md._

  Fig. 34
]

[Illustration:

  Fig. 35
]

Dew is a pretty good sign of fine weather. When you can see and hear
with remarkable clearness, and everything is calm and still, it is a
pretty infallible sign that cold weather is due.

Frost may be looked for on clear, calm, cloudless nights, when the
ground is apt to be cooler than the air.


                     INDICATIONS FROM CIRRUS CLOUDS

When these clouds suddenly appear in the sky on a clear summer day, they
indicate wet weather. Especially if the weather ends turn upward, which
means that the clouds are coming down. When moisture in the form of
little drops cling to vegetation, it is a pretty good indication that
there is apt to be more rain.

When the sky assumes the appearance of a gray mass and the sun is
observed shining through, it is a pretty good indication that it will
rain before night.

When overhead clouds are thick and grayish and the lower surface of them
is lumpy, this is an indication of rain.

Whirlwinds of dust are also indications of rain.


                                THE MOON

The rings that we see formed about the moon are caused by the delicate
white clouds through which the moon is shining.

[Illustration:

  _Courtesy Julien Friez & Sons, Baltimore, Md._

  Fig. 36
]


                              THE RAINBOW

The morning rainbow indicates that a shower is in the west, but if the
rainbow is in the east it indicates that the shower has passed over.


                            BIRDS AND STORMS

There are certain actions of birds that indicate many things pertaining
to the weather that are interesting. It is probable that their ability
to fly into the air gives them a view of the horizon, that by instinct
they have been able to determine the atmospheric changes. For instance,
it is well known that if birds of long flight remain at their base, it
generally foretells a storm. The sudden silence of birds has been
referred to a great many times preceding a storm.

Barnyard fowls do many peculiar things that foretell certain weather
conditions. The crow flies low and in great circles, cawing loudly,
before approaching rain.

Sometimes the house fly is a pretty good barometer. Generally before a
storm they seem to light on everything, particularly persons, and we
call them “sticky.” Generally at these times they congregate in swarms.
Most everyone is familiar with the gnat. They are one of the few insects
that gives us indications and good signs, and when you see them forming
in groups and moving along in front of you, you may expect fair weather.

There are many other interesting facts and fairy tales about indications
by animals and insects, but there is nothing scientific about them. It
has been demonstrated that there is nothing conclusive to be drawn from
such signs, so we will not attempt to waste pages of this book
reiterating these fables.

Certain actions of insects and animals give indications and enable the
weather prophet to prophesy. The spider is a good example of an insect
prophet, and if you will observe him carefully, you will find that when
stormy weather is going to come on he shortens his webs, and if he
anticipates a long, hard storm, he not only shortens the strings that
hold up the web, but he strengthens them as well, and vice-versa, when
he anticipates fine weather, he lengthens his strands of the web. When
you see the spider cease his activities and he hangs pretty close to his
home, which is the center of the web, you will know that rain is
approaching. On the other hand, if he continues to spread about during a
storm, you can be pretty certain that it is not going to be of very long
duration.

The frog is a good example of an animal prophet. There is a green frog
which has been studied in Germany, which will come out of the water when
rainy weather or cold is approaching. Some observers have placed these
frogs in a glass jar with a landing provided so that he can come out of
the water when he wants to, and he is always observed high and dry above
the water several hours in advance of a storm.




                          DEFINITE CONCLUSIONS
              Forecasting Weather by Means of Instruments


The first part of this book may not appeal to you, if you are of a
scientific trend of mind, but it is quite essential that you possess a
knowledge of the fundamentals treated in the earlier pages in order to
thoroughly understand the weather instruments we will now describe.
These instruments are the scientific means of forecasting what the
weather is going to be. They definitely indicate certain things, and
from these indications you are going to be able to draw conclusions and
become a scientist or meteorologist. The success that you attain will
depend upon the accuracy of the instruments and the care you use in
reading them. You will be able to rig up a Weather Bureau of your own,
and the use of these instruments will interest anyone in a study of the
weather.


                            THE WEATHER VANE

To make a forecast, it is essential from what we have already written,
to know the direction of the wind, and to determine the direction we
must have a weather vane. It is real important that the vane should be
sensitive to the slightest movement of the wind and give actual wind
directions. At the same time it must possess the property of steadiness,
so that when it is set up it will be rigid.

Fig. 34 shows the standard weather vane used at all United States
Weather Bureau Stations and Fig. 35 shows the Gilbert Weather Vane.

Fig. 35. The Gilbert weather vane consists of a metal arrow pointer and
a metal rod eight inches long and five thirty-seconds of an inch in
diameter. The rod is fastened by means of a few staples to the side of a
pole, or whatever is to be used as a support for the vane. About three
inches from the top of the rod is a collar with set screw, which is
tightened, and the vane itself is then placed on the rod, the rod
passing through the small angles A and B, between the sides of the vane.
It will be found that the vane will swing freely on this support, and by
constructing two crosspieces with letters N, S, E, and W at each end of
the pieces, of course having N pointing directly north, the vane will
swing around and show the direction of the wind.

[Illustration:

  Fig. 37
]

The standard United States Weather Bureau type hardly needs explanation,
as the illustration clearly shows all parts. It is the old, reliable,
standard iron, combined wind vane and anemometer support complete,
twenty feet high; iron contact box near base, improved roller bearings
for six-foot vane; latter, with electrical contacts shown enlarged at
the right. The vane is fastened securely to the roof of the building and
held in a perfectly vertical position.


                        THE ANEMOMETER. Fig. 36

It is essential to know the velocity of the wind. This is determined by
means of an instrument called the anemometer.

Fig. 36. The Standard U. S. Weather Bureau Station Anemometer.

This is the well-known standard Robinson Anemometer, now in universal
use throughout the world for the registration of wind velocity, but of
the latest improved construction. It records electrically the miles or
kilometers, etc., of wind movements on a register. The standard pattern
as furnished to Weather Bureau stations is made of brass, highly
polished and finished, aluminum (or copper reinforced) cups, steel
spindle with hard steel bearings, a ten-mile or kilometer indicator,
electrical contacts, etc.

[Illustration:

  Fig. 38
]

The four hollow hemispherical cups are mounted upon cross-arms at right
angles to each other, with the open sections vertical and facing the
same way around the circumference. The cross-arms are on a vertical
axis, which has at its lower end an endless screw. This axis is
supported so as to turn with as little friction as possible. The endless
screw is in gear with a wheel which moves two dials registering the
number of revolutions of the cups. The mechanisms are mounted in a
suitable metal case with glass front, as shown in the illustration, well
protected from the weather, the whole being designed for outdoor use.

[Illustration:

  _Courtesy Julien Friez & Sons, Baltimore, Md._

  Fig. 39
]

The center of the cups moves with a velocity about one-third that of the
wind which puts them in motion. The cups are four inches in diameter.
The distance from center of cup to center of rotation or axis is 6.72
inches. Assuming that the wind-travel is exactly three times that of the
center of the cup, the dials are marked to register miles of wind
travel, five hundred revolutions of the cups corresponding to a mile.

The ratio of wind-travel to travel of cup is in reality variable,
depending on the velocity of the wind. It is less for high than low
velocities. It varies also with the dimensions of the instrument, being
different for every different length of arm and diameter of cup.

On account of the great interference offered by buildings and other
obstructions to the free movement of the wind, its velocity is much less
in the vicinity of these obstructions than beyond; therefore, in
selecting the location for an anemometer, preference should be given to
the more elevated points in the vicinity of the station, and some rigid
support should be used to raise the instrument as far as practicable
above the immediate influence of the office building itself. The support
must be set up so that the anemometer on top or on the cross-arm is as
nearly vertical as possible.

The illustration shows clearly the appearance of an approved Weather
Bureau pattern combined support for wind instruments, similar to the one
installed at our plant.

[Illustration:

  Fig. 40
]

[Illustration:

  _Courtesy Taylor Instrument Companies Rochester, N. Y._

  Fig. 41
]

Fig. 37. The Gilbert Anemometer.

The Gilbert Anemometer consists of a case containing a spindle passing
through a worm gear, which turns a toothed gear. This gear in its rotary
motion makes a contact with a brass brush, which is connected
electrically with a flashlight. The cross-arms, with cups attached, is
placed on the spindle, and as the wind blows, it revolves the cups,
causing the contact. The velocity of the wind is determined by counting
the flashes for fifteen seconds, thus giving you the number of miles per
hour. For instance, if light flashes eight times in fifteen seconds,
this signifies that the wind is blowing eight miles an hour.

Fig. 38. How to Connect the Gilbert Anemometer.

By referring to the diagram, you will see that one wire which should be
the annunciator wire, or even a small electric light wire, is connected
from the wire at the anemometer case directly to one side of the lamp
socket. Another piece of the same size wire connects the other side of
the lamp socket to one terminal of your switch. The second terminal of
the switch should be connected to an outer post of one dry battery. The
inner post of this same dry battery should be connected to the outer
post of the second dry battery. Complete the circuit by connecting the
inner post of the second dry battery to any one of the screws at the
bottom of the anemometer case. The lamp used should be a small
flashlight battery lamp for use on two and a half to three volts. Be
sure in making the connections that the ends of your wire are scraped
free from insulation and dirt. This can be done by cutting off the
insulation with a knife and then rubbing the copper wire bright by a
piece of sandpaper or emery cloth, or even a file. The switch should be
left open when you are not taking readings, in order to prolong the life
of your batteries. By unloosening the little screw in the hub of the
anemometer vanes, you can remove them and also take off the brass cap on
the anemometer case. This should be taken apart once or twice a month,
and some machine oil used around the bearings to keep them from wearing
out too quickly.


   THE STANDARD ELECTRICAL SUNSHINE RECORDER AND THE GILBERT SUNSHINE
                                RECORDER

Fig. 39. The standard sunshine recorder is designed for recording the
duration of sunshine electrically, continuously, and automatically, on a
register. The instrument is essentially a differential air thermometer
in the form of a straight glass tube with cylindrical bulbs at each end,
enclosed in a protecting glass sheath, with suitable platinum wire
electrodes fused in at the center, the whole mounted in a metal socket
on an adjustable support.

[Illustration:

  _Courtesy Taylor Instrument Companies, Rochester, N. Y._

  Fig. 42
]

The base is secured to the support on the roof so that the glass tube
points north and south, with the blackened bulb toward the south and
lowermost, then the tube is inclined at such an angle that the
instrument will begin and cease to record sunshine with the proper
degree of cloudiness. This inclination should be approximately 45° from
the vertical. The machine should be adjusted at an hour when the sun is
wholly obscured.

In temperate and cold climates, slightly different adjustments will be
found necessary at different seasons of the year.

Fig. 40. The Gilbert Sunshine Recorder consists of a metal case,
cylindrical in form, with a piece of metal turned up on the ends,
dividing the cylinder in half. On each side of the case are small holes
through which the sun casts its rays and records its movement and
duration on a small piece of blue print paper inside the cylinder, one
piece of paper being in each compartment. When the blue print paper is
dipped in water, it becomes entirely bleached, with the exception of the
path made by the sun, which shows up in a blue line.

[Illustration:

  _Courtesy Julien Friez & Sons, Baltimore, Md._

  Fig. 43
]

[Illustration:

  _Courtesy Julien Friez & Sons, Baltimore, Md._

  Fig. 44
]

The sunshine recorder should be set up so that the ends point directly
north and south. The holes pierced in the sides of the case are nearer
one end than the other. The end that the holes are nearest should be
toward the south. It should be held firmly in place.


                             THE BAROMETER

The barometer is used for measuring the pressure of the atmosphere. The
principle of this instrument was first discovered by Torricelli, a pupil
of Galileo, the great Italian philosopher and scientist, in 1643. Many
and various types of instruments have been made, but the two most
generally used, especially where accurate indications are desired, are
the mercurial and aneroid barometers. Either of these instruments are
quite sensitive to changes in the weight or pressure of the earth’s
atmosphere, and from their variations we are able to draw conclusions
relative to changes in the weather. Figs. No. 41 and 42 illustrate the
standard mercurial and aneroid barometers used most extensively today. A
description of these barometers will serve to make the photographs
clearer to the readers of this text.


                   THE MERCURIAL BAROMETER (Fig. 41)

The mercurial barometer in use today is practically the same as that
invented by Torricelli. Of course, many changes have been made in the
case containing the tube of mercury, adding to its attractiveness, but
the principle remains the same.

The standard mercurial barometer consists of a straight glass tube about
thirty-two or thirty-three inches in length, hermetically sealed at one
end. The tube is of half-inch bore and is filled with chemically pure
mercury, which has been boiled in the tube to insure the total exclusion
of all air and moisture. After the tube has been filled, the open end is
immersed in a cistern of mercury. Upon immersion the mercury drops in
the tube to a height of 29.92 inches at sea level, or until
counterbalanced by the weight of the surrounding atmosphere pressing
upon the surface of the mercury in the cistern. The space in the top of
the tube is a perfect vacuum and is called the Torricellian vacuum.

The glass mercury tube is enclosed in a brass case. About two inches
from the top of the case is an opening extending down the front and back
for a distance of about eight inches. On each side of this opening is a
graduated scale, one side being in inches and the other graduated in
centimeters. The opening is fitted with a sliding vernier scale
graduated in millimeters, thus permitting the reading of changes in the
height of the mercury column most accurately, as the sliding vernier may
be adjusted to the level of the mercury by means of a thumb screw fitted
on the side of the case. The cistern containing the mercury is of glass,
with a soft leather or chamois bottom and an adjusting screw, used to
raise or lower the level of the mercury, so that it just comes in
contact with a small ivory point, inserted in the top of the cistern,
and which is used to mark the zero of the scale. Observations of the
changes in the atmospheric pressure should be taken at regular
intervals, and it is necessary to adjust the height of the mercury in
the cistern before each observation. This is done by bringing the ivory
point in contact with the level of the mercury and then bringing the
vernier scale absolutely level with the top of the column of mercury in
the tube, and then take the reading.

The mercurial barometer is a very delicate instrument and when once
placed in the desired position should not be moved. Care should be taken
that the room in which the barometer is placed is of nearly uniform
temperature, for if the temperature at the top of the barometer is
different than the temperature at the bottom, of course there will be an
effect produced on the changes in the mercury column. All other
barometers are set by the mercurial.


                    THE ANEROID BAROMETER (Fig. 42).

The aneroid barometer is so constructed that it contains no liquid
whatever, and thus derives its name from the Greek compound word
“aneroid,” meaning “without fluid.”

The essential parts of the instrument are a metallic case from which the
air has been exhausted, and which contains a spring. The case of elastic
metal is fastened to a base plate at the bottom and to the spring at the
top. The pressure of the atmosphere causes the case to expand and
contract, thus affecting the spring, which is connected to a needle or
dial, causing the dial to move around on the scale on the face of the
instrument and record the changes. The scale is marked off in inches
from 28 to 31, and besides a brass hand or pointer, used to designate
the changes in the atmospheric pressure, there is a small index hand to
set over the needle so that the amount of change in a certain period is
easily known on consulting the instrument.

[Illustration:

  _Courtesy Julien Friez & Sons, Baltimore, Md._

  Fig. 45
]

The dial of the barometer is marked with the words “Fair,” “Change,” and
“Rain,” etc., but these words have no significance, and should be
disregarded. For instance, 29½ is marked “Change”; 30, “Fair”; 31, “Very
dry”; 28½, “Rain.” If the barometer, which has been standing at 30.9,
suddenly drops down to 29.9, this is positive indication that a storm is
approaching, with strong winds, yet, according to the dial on the
aneroid, the reading would be “Fair.” If the barometer were standing at
28 and rose to 29, this would actually indicate approach of cold, dry
weather, and yet on the dial it reads “Rain.” This simply goes to show
that the readings on the dial are of no significance whatsoever, and are
not to be relied upon.

The aneroid is not as accurate an instrument as the mercurial, so should
be checked up occasionally with the mercurial barometer.

[Illustration:

  _Courtesy Taylor Instrument Companies Rochester, N. Y._

  Fig. 46
]

The aneroid type of barometer is also used in altitude work, but must be
compensated before using.

This type of barometer possesses several advantages over the mercurial
in that it is portable and therefore used for altitude work; at sea it
is used because there is no fluid to become unsettled by the motion of
the vessel; it is used also in observatory work because the action is
quicker than the mercurial barometer action, and sudden changes likely
to occur are indicated.


                     INDICATIONS FROM THE BAROMETER

A single observation reading of the barometer is of no significance.
Readings must be taken at different intervals or the results will be
misleading. The important thing about the barometer is to watch the rise
and fall, particularly, whether it is gradual or rapid. From no single
reading can you make an observation or a forecast. A rapid rise
indicates that a strong wind is apt to blow. A rapid fall indicates that
the weather will be unsettled, and that strong winds are apt to blow.
Both indicate a change in the weather, depending upon many things,
particularly, however, the direction from which the wind blows. If an
observer stands with the wind blowing on his back, the area of low
barometric pressure will be at his left, and that of high barometric
pressure at his right. With low pressure in the west and high pressure
in the east, the wind will be from the south; but with low pressure in
the east and high pressure in the west, the wind will be from the north.
The barometer rises for northerly winds, from northwest by the north to
eastward, for dry, or less wet weather, for less wind, or for more than
one of these changes—except on a few occasions, when rain, hail, or snow
comes from the northward with strong wind. The barometer falls for
southerly wind, from southeast, by the south, to the westward, for wet
weather, for stronger wind, or for more than one of these changes,
except on a few occasions, when moderate wind with rain or snow comes
from the northward.

                             RELATIVE HUMIDITY TABLES


                        _Per Cent Fahrenheit Temperatures_


            Difference in Degrees Between Wet and Dry Bulb Thermometers


 ═════╤═══╤═══╤═══╤═══╤═══╤═══╤═══╤═══╤═══╤════╤════╤════╤════╤════╤════╤════╤════
 Read-│1.0│2.0│3.0│4.0│5.0│6.0│7.0│8.0│9.0│10.0│11.0│12.0│13.0│14.0│15.0│16.0│17.0
  ing │   │   │   │   │   │   │   │   │   │    │    │    │    │    │    │    │
  of  │   │   │   │   │   │   │   │   │   │    │    │    │    │    │    │    │
  Dry │   │   │   │   │   │   │   │   │   │    │    │    │    │    │    │    │
 Bulb │   │   │   │   │   │   │   │   │   │    │    │    │    │    │    │    │
 Ther-│   │   │   │   │   │   │   │   │   │    │    │    │    │    │    │    │
 mom- │   │   │   │   │   │   │   │   │   │    │    │    │    │    │    │    │
 eter │   │   │   │   │   │   │   │   │   │    │    │    │    │    │    │    │
 ─────┼───┼───┼───┼───┼───┼───┼───┼───┼───┼────┼────┼────┼────┼────┼────┼────┼────
    32│ 90│ 79│ 69│ 60│ 50│ 41│ 31│ 22│ 13│   4│    │    │    │    │    │    │
    33│ 90│ 80│ 71│ 61│ 52│ 42│ 33│ 24│ 16│   7│    │    │    │    │    │    │
    34│ 90│ 81│ 72│ 62│ 53│ 44│ 35│ 27│ 18│   9│   1│    │    │    │    │    │
      │   │   │   │   │   │   │   │   │   │    │    │    │    │    │    │    │
    35│ 91│ 82│ 73│ 64│ 55│ 46│ 37│ 29│ 20│  12│   4│    │    │    │    │    │
    36│ 91│ 82│ 73│ 65│ 56│ 48│ 39│ 31│ 23│  14│   6│    │    │    │    │    │
    37│ 91│ 83│ 74│ 66│ 58│ 49│ 41│ 33│ 25│  17│   9│   1│    │    │    │    │
    38│ 91│ 83│ 75│ 67│ 59│ 51│ 43│ 35│ 27│  19│  12│   4│    │    │    │    │
    39│ 92│ 84│ 76│ 68│ 60│ 52│ 44│ 37│ 29│  21│  14│   7│    │    │    │    │
      │   │   │   │   │   │   │   │   │   │    │    │    │    │    │    │    │
    40│ 92│ 84│ 76│ 68│ 61│ 53│ 46│ 38│ 31│  23│  16│   9│   2│    │    │    │
    41│ 92│ 84│ 77│ 69│ 62│ 54│ 47│ 40│ 33│  26│  18│  11│   5│    │    │    │
    42│ 92│ 85│ 77│ 70│ 62│ 55│ 48│ 41│ 34│  28│  21│  14│   7│    │    │    │
    43│ 92│ 85│ 78│ 70│ 63│ 56│ 49│ 43│ 36│  29│  23│  16│   9│   3│    │    │
    44│ 93│ 85│ 78│ 71│ 64│ 57│ 51│ 44│ 37│  31│  24│  18│  12│   5│    │    │
      │   │   │   │   │   │   │   │   │   │    │    │    │    │    │    │    │
    45│ 93│ 86│ 79│ 71│ 65│ 58│ 52│ 45│ 39│  33│  26│  20│  14│   8│   2│    │
    46│ 93│ 86│ 79│ 72│ 65│ 59│ 53│ 46│ 40│  34│  28│  22│  16│  10│   4│    │
    47│ 93│ 86│ 79│ 73│ 66│ 60│ 54│ 47│ 41│  35│  29│  23│  17│  12│   6│   1│
    48│ 93│ 87│ 80│ 73│ 67│ 60│ 54│ 48│ 42│  36│  31│  25│  19│  14│   8│   3│
    49│ 93│ 87│ 80│ 74│ 67│ 61│ 55│ 49│ 43│  37│  32│  26│  21│  15│  10│   5│
      │   │   │   │   │   │   │   │   │   │    │    │    │    │    │    │    │
    50│ 93│ 87│ 81│ 74│ 68│ 62│ 56│ 50│ 44│  39│  33│  28│  22│  17│  12│   7│   2
    51│ 94│ 87│ 81│ 75│ 69│ 63│ 57│ 51│ 45│  40│  35│  29│  24│  19│  14│   9│   4
    52│ 94│ 88│ 81│ 75│ 69│ 63│ 58│ 52│ 46│  41│  36│  30│  25│  20│  15│  10│   6
    53│ 94│ 88│ 82│ 75│ 70│ 64│ 58│ 53│ 47│  42│  37│  32│  27│  22│  17│  12│   7
    54│ 94│ 88│ 82│ 76│ 70│ 65│ 59│ 54│ 48│  43│  38│  33│  28│  23│  18│  14│   9
      │   │   │   │   │   │   │   │   │   │    │    │    │    │    │    │    │
    55│ 94│ 88│ 82│ 76│ 71│ 65│ 60│ 55│ 49│  44│  39│  34│  29│  25│  20│  15│  11
    56│ 94│ 88│ 82│ 77│ 71│ 66│ 61│ 55│ 50│  45│  40│  35│  31│  26│  21│  17│  12
    57│ 94│ 88│ 83│ 77│ 72│ 66│ 61│ 56│ 51│  46│  41│  36│  32│  27│  23│  18│  14
    58│ 94│ 89│ 83│ 77│ 72│ 67│ 62│ 57│ 52│  47│  42│  38│  33│  28│  24│  20│  15
    59│ 94│ 89│ 83│ 78│ 73│ 68│ 63│ 58│ 53│  48│  43│  39│  34│  30│  25│  21│  17
      │   │   │   │   │   │   │   │   │   │    │    │    │    │    │    │    │
    60│ 94│ 89│ 84│ 78│ 73│ 68│ 63│ 58│ 53│  49│  44│  40│  35│  31│  27│  22│  18
    61│ 94│ 89│ 84│ 79│ 74│ 68│ 64│ 59│ 54│  50│  45│  40│  36│  32│  28│  24│  20
    62│ 94│ 89│ 84│ 79│ 74│ 69│ 64│ 60│ 55│  50│  46│  41│  37│  33│  29│  25│  21
    63│ 95│ 90│ 84│ 79│ 74│ 70│ 65│ 60│ 56│  51│  47│  42│  38│  34│  30│  26│  22
    64│ 95│ 90│ 85│ 79│ 75│ 70│ 66│ 61│ 56│  52│  48│  43│  39│  35│  31│  27│  23
      │   │   │   │   │   │   │   │   │   │    │    │    │    │    │    │    │
    65│ 95│ 90│ 85│ 80│ 75│ 70│ 66│ 62│ 57│  53│  48│  44│  40│  36│  32│  28│  25
    66│ 95│ 90│ 85│ 80│ 76│ 71│ 66│ 62│ 58│  53│  49│  45│  41│  37│  33│  29│  26
    67│ 95│ 90│ 85│ 80│ 76│ 71│ 67│ 62│ 58│  54│  50│  46│  42│  38│  34│  30│  27
    68│ 95│ 90│ 85│ 81│ 76│ 72│ 67│ 63│ 59│  55│  51│  47│  43│  39│  35│  31│  28
    69│ 95│ 90│ 86│ 81│ 77│ 72│ 68│ 64│ 59│  55│  51│  47│  44│  40│  36│  32│  29
      │   │   │   │   │   │   │   │   │   │    │    │    │    │    │    │    │
    70│ 95│ 90│ 86│ 81│ 77│ 72│ 68│ 64│ 60│  56│  52│  48│  44│  40│  37│  33│  30
    71│ 95│ 90│ 86│ 82│ 77│ 73│ 69│ 64│ 60│  56│  53│  49│  45│  41│  38│  34│  31
    72│ 95│ 91│ 86│ 82│ 78│ 73│ 69│ 65│ 61│  57│  53│  49│  46│  42│  39│  35│  32
    73│ 95│ 91│ 86│ 82│ 78│ 73│ 69│ 65│ 61│  58│  54│  50│  46│  43│  40│  36│  33
    74│ 95│ 91│ 86│ 82│ 78│ 74│ 70│ 66│ 62│  58│  54│  51│  47│  44│  40│  37│  34
      │   │   │   │   │   │   │   │   │   │    │    │    │    │    │    │    │
    75│ 96│ 91│ 87│ 82│ 78│ 74│ 70│ 66│ 63│  59│  55│  51│  48│  44│  41│  38│  34
    76│ 96│ 91│ 87│ 83│ 78│ 74│ 70│ 67│ 63│  59│  55│  52│  48│  45│  42│  38│  35
    77│ 96│ 91│ 87│ 83│ 79│ 75│ 71│ 67│ 63│  60│  56│  52│  49│  46│  42│  39│  36
    78│ 96│ 91│ 87│ 83│ 79│ 75│ 71│ 67│ 64│  60│  57│  53│  50│  46│  43│  40│  37
    79│ 96│ 91│ 87│ 83│ 79│ 75│ 71│ 68│ 64│  60│  57│  54│  50│  47│  44│  41│  37
      │   │   │   │   │   │   │   │   │   │    │    │    │    │    │    │    │
    80│ 96│ 91│ 87│ 83│ 79│ 76│ 72│ 68│ 64│  61│  57│  54│  51│  47│  44│  41│  38
    82│ 96│ 92│ 88│ 84│ 80│ 76│ 72│ 69│ 65│  62│  58│  55│  52│  49│  46│  43│  40
    84│ 96│ 92│ 88│ 84│ 80│ 77│ 73│ 70│ 66│  63│  59│  56│  53│  50│  47│  44│  41
    86│ 96│ 92│ 88│ 85│ 81│ 77│ 74│ 70│ 67│  63│  60│  57│  54│  51│  48│  45│  42
    88│ 96│ 92│ 88│ 85│ 81│ 78│ 74│ 71│ 67│  64│  61│  58│  55│  52│  49│  46│  43
      │   │   │   │   │   │   │   │   │   │    │    │    │    │    │    │    │
    90│ 96│ 92│ 89│ 85│ 81│ 78│ 75│ 71│ 68│  65│  62│  59│  56│  53│  50│  47│  44
    92│ 96│ 92│ 89│ 85│ 82│ 78│ 75│ 72│ 69│  65│  62│  59│  57│  54│  51│  48│  45
    94│ 96│ 93│ 89│ 86│ 82│ 79│ 75│ 72│ 69│  66│  63│  60│  57│  54│  52│  49│  46
    96│ 96│ 93│ 89│ 86│ 82│ 79│ 76│ 73│ 70│  67│  64│  61│  58│  55│  53│  50│  47
    98│ 96│ 93│ 89│ 86│ 83│ 79│ 76│ 73│ 70│  67│  64│  61│  59│  56│  53│  51│  48
      │   │   │   │   │   │   │   │   │   │    │    │    │    │    │    │    │
   100│ 96│ 93│ 90│ 86│ 83│ 80│ 77│ 74│ 71│  68│  65│  62│  59│  57│  54│  52│  49
 ─────┴───┴───┴───┴───┴───┴───┴───┴───┴───┴────┴────┴────┴────┴────┴────┴────┴────

[Illustration:

  _Courtesy Taylor Instrument Companies, Rochester, N.Y._

  Fig. 47

  Like the hygrometer, this instrument measures the “relative humidity.”
]

[Illustration:

  Fig. 48

  GILBERT HYGROMETER
]


                     GENERAL BAROMETER INDICATIONS

A gradual but steady rise indicates settled fair weather.

A gradual but steady fall indicates unsettled or wet weather.

A very slow rise from a low point is usually associated with high winds
and dry weather.

A rapid rise indicates clear weather with high winds.

A very slow fall from a high point is usually connected with wet and
unpleasant weather without much wind.

The following table of the United States Weather Bureau gives a summary
of the wind and barometer indications:

 Barometer Reduced to Sea Level   Wind    Character of Weather Indicated
                                Direction

 ───────────────────────────────────────────────────────────────────────
 30.10 to 30.20 and steady      SW to NW  Fair with slight temperature
                                            changes for 1 to 2 days
 30.10 to 30.20 and rising      SW to NW  Fair, followed within 2 days
   rapidly                                  by warmer and rain
 30.10 to 30.20 and falling     SW to NW  Warmer, with rain in 24 to 36
   slowly                                   hours
 30.10 to 30.20 and falling     SW to NW  Warmer, with rain in 18 to 24
   rapidly                                  hours
 30.20 and above and stationary SW to NW  Continued fair, with no
                                            decided temperature change
 30.20 and above and falling    SW to NW  Slowly rising temperature and
   slowly                                   fair for two days
 30.10 to 30.20 and falling     S to SE   Rain within 24 hours
   slowly
 30.10 to 30.20 and falling     S to SE   Wind increasing in force, with
   rapidly                                  rain within 12 to 24 hours
 30.10 to 30.20 and falling     SE to NE  Rain in 12 to 18 hours
   slowly
 30.10 to 30.20 and falling     SE to NE  Increasing wind, with rain
   rapidly                                  within 12 hours
 30.10 and above and falling    E to NE   In summer, with light winds,
   slowly                                   rain may not fall for
                                            several days. In winter,
                                            rain within 24 hours
 30.10 and above and falling    E to NE   In summer, rain probably
   rapidly                                  within 12 to 24 hours. In
                                            winter, rain or snow, with
                                            increasing wind will often
                                            set in, when the barometer
                                            begins to fall and the wind
                                            sets in from the NE
 30 or below and falling slowly SE to NE  Rain will continue 1 or 2 days
 30 or below and falling        SE to NE  Rain, with high wind, followed
   rapidly                                  within 24 hours by clearing
                                            and cooler
 30 or below and rising slowly  S to SW   Clearing within a few hours
                                            and continued fair for
                                            several days
 29.80 or below and falling     S to E    Severe storm of wind and rain
   rapidly                                  or snow imminent, followed
                                            within 24 hours by clearing
                                            and colder
 29.80 or below and falling     E to N    Severe northeast gales and
   rapidly                                  heavy rain or snow, followed
                                            in winter by a cold wave
 29.80 or below and rising      Going to  Clearing and colder
   rapidly                      W

A sudden fall indicates a sudden shower or high winds, or both.

[Illustration:

  _Courtesy Julien Friez & Son Baltimore, Md._

  Fig. 49
  U. S. STANDARD RAIN GAUGE
]

A stationary barometer indicates a continuance of existing weather
conditions. (_Note_: Tap the barometer slightly on the face. If the
hands move a trifle, it indicates that there is the tendency to rise or
fall, depending upon the direction of movement of the hands.)

Northeasterly winds precede storms that approach from the southwest;
that is, in New England and the Middle States and the Ohio Valley.
Southeasterly winds precede storms that approach from the Lake region.


                              THERMOMETERS

For information regarding the manufacture of thermometers, we recommend
P. R. Jameson’s book, “Weather and Weather Instruments,” published by
the Taylor Instrument Companies of Rochester, N. Y.

Thermometers are of great importance to us in determining weather.


                        LOCATION OF THERMOMETERS

1. They must be properly exposed.

2. A good circulation of air around them is necessary.

3. They must be properly protected from the rays of the sun.

_Note_: If these instructions are not carefully followed out, errors are
apt to occur, and you will be misled.

For a change of wind towards northerly directions, a thermometer falls.
For a change of wind toward southerly directions a thermometer rises.

[Illustration:

  Fig. 50

  GILBERT RAIN GAUGE
]


                    MAXIMUM AND MINIMUM THERMOMETERS

Maximum and minimum thermometers are used to record the daily maximum
and minimum temperatures. Fig. 46 shows a typical maximum and minimum
thermometer used for giving the extremes of temperature. One side of the
thermometer has a scale reading, beginning at the top, from 60° below
zero to 140° above zero. This is the scale used when determining the
coldest temperature reached during a day. The other side of the
thermometer has a scale marked from 70° below zero, beginning at the
bottom and reading up, to 130° above zero. On this side the maximum heat
reached during the day is recorded. There is a small metal piece in the
tubes, one on each side, and as the mercury pushes ahead or recedes, the
small index is left at the lowest point reached in one tube and at the
highest point reached in the other. The small metal piece is drawn back
to the level of the mercury by means of a small magnet.


                  WHEN MAXIMUM TEMPERATURE IS REACHED

You can generally look for maximum temperature between three and four
o’clock in the afternoon. At this time the sun has reached its highest
altitude.

[Illustration:

  _Courtesy Julien Friez & Sons, Baltimore, Md._

  Fig. 51

  TIPPING BUCKET RAIN GAUGE
]


                WHEN THE MINIMUM TEMPERATURE IS REACHED

This usually occurs a little while before sunrise. It is important in
weather observing to make a record of the highest temperature of the day
and the lowest temperature of the night. Continuous observation, as the
reader will appreciate, is practically impossible for such a record.


                THE THERMOMETER FOR HUMIDITY IN THE AIR

Moisture or dampness in the air, as shown by an instrument called the
hygrometer, increases before rain, fog, or dew.

Before describing the hygrometer, a definition of a few of the terms
used in conjunction with the instrument will be found useful.


                           ABSOLUTE HUMIDITY

The amount of vapor actually present in the atmosphere is termed the
absolute humidity, expressed usually either in the expansive force that
the vapor exerts or in its weight in grains per cubic foot of air.


                           RELATIVE HUMIDITY

The absolute humidity divided by the amount of vapor that might exist if
the air were saturated gives a ratio that is called the relative
humidity.


                               DEW POINT

The temperature at which moisture begins to be condensed on a cold
vessel or other container and becomes visible is called the dew point.


                        HOW HYGROMETERS ARE MADE

The most generally used hygrometer consists of two ordinary
thermometers, the bulb of one being covered with a piece of muslin and
kept constantly moistened with water by means of a wick or cotton thread
communicating with a container of water. The difference in the readings
of the two thermometers, the wet and the dry, is observed, and knowing
this, it is very easy to determine the humidity by consulting a table
(see table on pages 58–59), which has been prepared for this purpose.
These instruments are, according to the increase in price, equipped with
a table, and the container is held in a wire frame, as you will see from
the Figs. 49–50 showing the standard Weather Bureau station instrument
and the Gilbert hygrometer.

Fig. 49 shows the U. S. Standard Weather Bureau Station Rain Gauge, Fig.
50 the Gilbert Rain Gauge and Fig. 51 the U. S. Standard Weather Bureau
Station Rain Gauge, Tipping Bucket Type.

The Gilbert Weather Station is equipped with the Tipping Bucket Type
Rain Gauge. Fig. 51 shows the apparatus clearly, complete and mounted
ready for use. The brass bucket seen in position through the open door
is adjusted to tip for each hundredth inch of rainfall collected in the
twelve-inch diameter receiver at the top, and this rainfall is
electrically recorded at any convenient distance on a register. After
any desired period the water may be drawn off and check measurements
made by means of the brass measuring tube and graduated cedar stick
shown in the figure.


                   THE GILBERT RAIN GAUGE (Fig. 50).

 (_a_) Tube.

 (_b_) Funnel.

 (_c_) Measuring stick.

The essential parts of the Gilbert Rain Gauge consists of a metal tube
twelve inches long, having a diameter of 1⁵⁄₁₆ inches (inside) and a
funnel-shaped top, the neck of which fits snugly into the open end of
the metal tube. The outside diameter of the neck of the funnel is a
trifle less than 1⁵⁄₁₆ inches. The area of the circle formed at the top
of the tube is one-tenth the area of the funnel circle. A measuring
stick is provided to measure the rainfall collected in the tube.

To determine the amount of rainfall on the surface of the ground, the
rain collected in the tube should be measured at regular intervals,
usually twelve hours apart. For every inch of rain collected in the
tube, as denoted by the measuring stick, it means that there is one
one-tenth of an inch of rain on the ground; if 10 inches of rain in the
tube, it signifies one inch of rain on the ground. In other words,
divide the figure recorded on the measuring stick by ten for actual
rainfall.

It is well to put some sort of a shelter around the gauge, so that it
will be protected from strong winds. The shelter is usually placed at a
distance from the tube equal to the height of the tube. With the Gilbert
rain gauge it is well to erect the shelter at a distance of about three
feet from the tube. It is essential that the gauge be held in an upright
position, so it should be fastened to the roof.

Snow is measured by melting the quantity collected in the gauge and
follow the same procedure as in rainfall measurements.

There is another very common method, called ground measurement. There
are many instances where ground measurements are inaccurate:

1. When snow and rain are mixed or alternate.

2. When melting accompanies snowfall.

3. When snow is already upon the ground.

4. When the amount of fall is very small.

5. When drifting is very bad.

6. When the snow is blown about after the storm and before measurements
have been made.

A bucket and a spring balance are used. The bucket is filled with snow,
but not packed down too hard, and weighed. The reading of the index hand
on the spring balance gives the density of the snow. The depth of the
snow in the vicinity of the spot from which the bucket was filled is
obtained and this figure is multiplied by the density, thus giving the
water equivalent of the snow collected. For instance, if the reading of
the balance was .16, and the depth of the snow was 7 inches, multiply
.16 by 7, and the result, 1.12, is the water equivalent of the snow.


                           THERMOMETER SCALES

The first thermometer scale to give satisfaction was devised in 1714 by
Fahrenheit. He determined the fixed points on the thermometer in a very
novel manner. Having been born at Dantzig, he took for the zero point on
his scale the lowest temperature observed by him at Dantzig, which he
found was that produced by mixing equal quantities of snow and
sal-ammoniac. The space between this point and that to which the mercury
rose at the temperature of boiling water he divided into 212 parts. He
determined, with his thermometer, that the atmospheric pressure governed
the boiling point of water. Today the Fahrenheit thermometer is used
extensively, and has for its freezing point 32° and for its boiling
point 212°.

Another scale that has not become too well known, because of the fact
that it did not meet with public favor, was devised by a Frenchman,
named Reaumur, in 1730, and bears his name. He determined the freezing
point of the scale at 0° and the boiling point of water at 80°.

Another Frenchman, named Anders Celsius, devised a scale with the
boiling point of water at 0° and the freezing point at 100°. In 1743 a
Frenchman, named Christin, living at Lyons, France, reversed the points,
and today the scale is known as the Centigrade scale, and, together with
the Fahrenheit scale, is used almost exclusively wherever thermometers
are required.


                  HOW TO CHANGE ONE SCALE INTO ANOTHER

Centigrade degrees into Fahrenheit: multiply by 9, divide the product by
5 and add 32.

Fahrenheit degrees into Centigrade: subtract 32, multiply by 5, and
divide by 9.

Reaumur degrees into Fahrenheit: multiply by 9, divide by 4, and add 32.

Fahrenheit degrees into Reaumur: subtract 32, multiply by 4, and divide
by 9.

Reaumur degrees into Centigrade: multiply by 5 and divide by 4.

Centigrade degrees into Reaumur: multiply by 4 and divide by 5.


  WEATHER BUREAU STATIONS OF THE UNITED STATES AND WEATHER BUREAU MAPS

The following is a list of the Weather Bureau Stations of the United
States, and from any of these offices, preferably the one nearest you,
you will be able to obtain the weather reports and weather map (see Fig.
52), indicating many things of interest, and from which you will be able
to make a careful study of the weather.

 ABILENE, TEX.
 ALBANY, N. Y.
 ALPENA, MICH.
 AMARILLO, TEX.
 ANNISTON, ALA.
 ASHEVILLE, N. C.
 ATLANTA, GA.
 ATLANTIC CITY, N. J.
 AUGUSTA, GA.
 BAKER, ORE.
 BALTIMORE, MD.
 BENTONVILLE, ARK.
 BINGHAMTON, N. Y.
 BIRMINGHAM, ALA.
 BISMARCK, N. D.
 BLOCK ISLAND, R. I.
 BOISE, IDA.
 BOSTON, MASS.
 BROKEN ARROW, OKLA.
 BUFFALO, N. Y.
 BURLINGTON, VT.
 CAIRO, ILL.
 CANTON, N. Y.
 CAPE HENRY, VA.
 CAPE MAY, N. J.
 CHARLES CITY, IA.
 CHARLESTON, S. C.
 CHARLOTTE, N. C.
 CHATTANOOGA, TENN.
 CHEYENNE, WYO.
 CHICAGO, ILL.
 CINCINNATI, OHIO
 CLALLAM BAY, WASH.
 CLEVELAND, OHIO
 COLUMBIA, MO.
 COLUMBIA, S. C.
 COLUMBUS, OHIO
 CONCORD, N. H.
 CONCORDIA, KANS.
 CORPUS CHRISTI, TEX.
 DALLAS, TEX.
 DAVENPORT, IA.
 DAYTON, OHIO
 DEL RIO, TEX.
 DENVER, COLO.
 DES MOINES, IA.
 DETROIT, MICH.
 DEVILS LAKE, NO. DAK.
 DODGE CITY, KANS.
 DREXEL, NEB.
 DUBUQUE, IA.
 DULUTH, MINN.
 EASTPORT, ME.
 ELKINS, W. VA.
 ELLENDALE, NO. DAK.
 EL PASO, TEX.
 ERIE, PA.
 ESCANABA, MICH.
 EUREKA, CAL.
 EVANSVILLE, IND.
 FORT SMITH, ARK.
 FORT WAYNE, IND.
 FORT WORTH, TEX.
 FRESNO, CAL.
 GALVESTON, TEX.
 GRAND HAVEN, MICH.
 GRAND JUNCTION, COLO.
 GRAND RAPIDS, MICH.
 GREEN BAY, WIS.
 GREENVILLE, S. C.
 GROESBECK, TEX.
 HANNIBAL, MO.
 HARRISBURG, PA.
 HARTFORD, CONN.
 HATTERAS, N. C.
 HAVRE, MONT.
 HELENA, MONT.
 HONOLULU, HAWAII
 HOUGHTON, MICH.
 HOUSTON, TEX.
 HURON, SO. DAK.
 INDEPENDENCE, CAL.
 INDIANAPOLIS, IND.
 IOLA, KANS.
 ITHACA, N. Y.
 JACKSONVILLE, FLA.
 JUNEAU, ALASKA
 KALISPELL, MONT.
 KANSAS CITY, MO.
 KEOKUK, IOWA
 KEY WEST, FLA.
 KILAUEA, HAWAII
 KNOXVILLE, TENN.
 LA CROSSE, WIS.
 LANDER, WYO.
 LANSING, MICH.
 LEESBURG, GA.
 LEWISTON, IDAHO
 LEXINGTON, KY.
 LINCOLN, NEB.
 LITTLE ROCK, ARK.
 LOS ANGELES, CAL.
 LOUISVILLE, KY.
 LUDINGTON, MICH.
 LYNCHBURG, VA.
 MACON, GA.
 MADISON, WIS.
 MANTEO, N. C.
 MARQUETTE, MICH.
 MEMPHIS, TENN.
 MERIDIAN, MISS.
 MIAMI, FLA.
 MILWAUKEE, WIS.
 MINNEAPOLIS, MINN.
 MOBILE, ALA.
 MODENA, UTAH
 MONTGOMERY, ALA.
 MOUNT TAMALPAIS, CAL.
 NANTUCKET, MASS.
 NASHVILLE, TENN.
 NEAH BAY, WASH.
 NEW HAVEN, CONN.
 NEW ORLEANS, LA.
 NEW YORK, N. Y.
 NORFOLK, VA.
 NORTHFIELD, VT.
 NORTH HEAD, WASH.
 NORTH PLATTE, NEB.
 OKLAHOMA, OKLA.
 OMAHA, NEB.
 OSWEGO, N. Y.
 PALESTINE, TEX.
 PARKERSBURG, W. VA.
 PENSACOLA, FLA.
 PEORIA, ILL.
 PHILADELPHIA, PA.
 PHOENIX, ARIZ.
 PIERRE, SO. DAK.
 PITTSBURGH, PA.
 POCATELLO, IDAHO
 POINT REYES LIGHT, CAL.
 PORT ANGELES, WASH.
 PORT ARTHUR, TEX.
 PORT HURON, MICH.
 PORTLAND, ME.
 PORTLAND, ORE.
 PROVIDENCE, R. I.
 PUEBLO, COLO.
 RALEIGH, N. C.
 RAPID CITY, SO. DAK.
 READING, PA.
 RED BLUFF, CAL.
 RENO, NEV.
 RICHMOND, VA.
 ROCHESTER, N. Y.
 ROSEBURG, ORE.
 ROSWELL, NEW MEX.
 ROYAL CENTER, IND.
 SACRAMENTO, CAL.
 SAGINAW, MICH.
 ST. JOSEPH, MO.
 ST. LOUIS, MO.
 ST. PAUL, MINN.
 SALT LAKE CITY, UTAH
 SAN ANTONIO, TEX.
 SAN DIEGO, CAL.
 SAND KEY, FLA.
 SANDUSKY, OHIO
 SANDY HOOK, N. J.
 SAN FRANCISCO, CAL.
 SAN JOSE, CAL.
 SAN JUAN, PORTO RICO
 SAN LUIS OBISPO, CAL.
 SANTA FE, NEW MEX.
 SAULT SAINTE MARIE, MICH.
 SAVANNAH, GA.
 SCRANTON, PA.
 SEATTLE, WASH.
 SEKIOU, WASH.
 SHERIDAN, WYO.
 SHREVEPORT, LA.
 SIOUX CITY, IOWA
 SPOKANE, WASH.
 SPRINGFIELD, ILL.
 SPRINGFIELD, MO.
 SYRACUSE, N. Y.
 TACOMA, WASH.
 TAMPA, FLA.
 TATOOSH ISLAND, WASH.
 TAYLOR, TEX.
 TERRE HAUTE, IND.
 THOMASVILLE, GA.
 TOLEDO, OHIO
 TONOPAH, NEV.
 TOPEKA, KANS.
 TRENTON, N. J.
 TWIN, WASH.
 VALENTINE, NEB.
 VICKSBURG, MISS.
 WAGON WHEEL GAP, COLO.
 WALLA WALLA, WASH.
 WICHITA, KANS.
 WILLISTON, NO. DAK.
 WILMINGTON, N. C.
 WINNEMUCCA, NEV.
 WYTHEVILLE, VA.
 YANKTON, SO. DAK.
 YELLOWSTONE PARK, WYO.
 YUMA, ARIZ.

You will notice that on this map different lines are drawn: First, the
Isobar lines—these are solid lines drawn through places which have the
same barometric pressure. Second, the Isotherm lines—these are dotted
lines drawn through places having the same temperature.

The Weather Bureau Maps are gotten out on the same day all over the
country, and the preparation of them is quite interesting.

At 7:40 A. M. simultaneous readings are taken at all weather bureau
stations of the country. On the coast, where the time is three hours
different than at New York, the readings are taken at 4:40, so that the
hour corresponds at all places. At 8:00 A. M. the various stations
telephone their findings to the Western Union Office located in their
city and immediately the messages are transmitted by Western Union to a
central district office, or circuit center as it is called. For New
England, the circuit center is Boston. All messages are received at this
office, and from here transmitted to the next office, which is New York,
and from New York to the next center, until the news is transmitted to
the coast. The wires are open from 8:00 until 9:30 A. M. The western
offices follow the same procedure until the weather indications are
received by all stations. Immediately the preparation of the map is
begun and they are mailed to interested parties by the Weather Bureau
Stations of the United States.

Figs. 52, 53 and 54 show three maps, typifying storms traveling from the
west to the east, and by studying them on successive days you can at
once grasp the importance of studying the weather from these maps.

Fig. 53 shows a storm of low pressure and how this area of low pressure
is progressing and moving from the west to the east. Particular notice
should be taken of how fast the storm travels, that is, the distance it
goes each day, and the direction it is going and the results.

[Illustration:

  Fig. 52
]

[Illustration:

  Fig. 53
]

[Illustration:

  Fig. 54
]

The arrows denote the direction of the wind, and you will notice they
point to the region of low barometric pressure. In the regions of high
barometric pressure the winds are in the opposite direction. This
readily explains to you why it is that you can expect changes in weather
conditions when the wind changes.

From the markings and printed matter on each map, information is secured
regarding observations of the barometer, thermometer, wind velocity,
direction of the wind, kind of clouds, and their movements, and the
amount of precipitation (rain or snow), in different localities.


               HOW THE STATE OF THE WEATHER IS INDICATED

Clear, partly cloudy, cloudy, rain or snow indications are symbolized.
The shaded area designates places or areas where precipitation has
occurred during the preceding twelve hours.


             WHAT THE WORDS “HIGH” OR “LOW” MEAN ON THE MAP

Low barometric pressure, or the storm centers, are indicated on the map
by the word “low.” High barometric pressure centers are indicated by the
word “high.” Note how they move in an easterly direction; how they are
progressive. They can be compared to a series of waves, which we will
call atmospheric waves. The crest of the wave may be likened to the
“highs” and the troughs to the “lows.”

Usually the winds are southerly or easterly and therefore warmer in
advance of a “low.” When the “lows” progress east of a place, the wind
generally shifts to westerly and the temperature lowers. The westward
advance of the “lows” is preceded by precipitation, and almost always in
the form of rain or snow, following which the weather is generally
clear. Note how a “low” is followed by a “high,” and so on as they move
along eastwardly.


                        WHAT ISOTHERMS INDICATE

If the Isotherms run nearly parallel, that is, east and west, there will
most likely be no change in the temperature. Southerly to east winds
prevail west of the nearly north and south line, passing through the
middle of a “high” and also east of a like line passing through the
middle of a “low.”

To the west of a nearly north and south line passing through the middle
of a “low,” northerly to westerly winds prevail. We will find the same
condition prevailing to the east of a line passing through the center of
a “high.”

[Illustration:

  Fig. 55
]

When we find an absence of decidedly energetic “lows” and “highs,” this
is an indication of the continuance of existing weather. We can expect
this state of the atmosphere until later maps show a beginning of a
change, usually first appearing in the west.


                 TRACKS OF STORMS IN THE UNITED STATES

The storms of the United States follow, however, year after year, a
series of tracks, not likely to change suddenly, and not irregular, but
related to each other by very well-defined laws.

The United States Weather Bureau has made a very intensive study of the
positions of the tracks of the storms. Fig. 55 shows the mean tracks and
the movement of storms from day to day. This map indicates that
generally there are two sets of lines running west and east, one set
over the northwestern boundary, the Lake region, and the St. Lawrence
Valley, the other set over the middle Rocky Mountain districts and the
Gulf States. Each of these is double, with one for the “highs” and one
for the “lows.” Furthermore, there are lines crossing from the main
tracks to join them together, showing how storms pass from one to the
other. On the chart, the heavy lines all belong to the tracks of the
“highs,” and the lighter lines to the track of the “lows.”


                   THE MODE OF TRAVEL OF THE “HIGHS”

A “high” reaching the California coast may cross the mountains near Salt
Lake City (follow the track on the map), and then pass directly over the
belt of the Gulf States, turning northeastward and reaching the Virginia
coast; or it may move farther northward, cross the Rocky Mountains in
the State of Washington, up the Columbia River Valley, then turn east,
and finally reach the Gulf of St. Lawrence. These tracks are located
where they are by the laws of general circulation of the atmosphere and
the outline of the North American continent. This movement of the
“highs” from the middle Pacific coast to Florida or to the Gulf of St.
Lawrence is confined to the summer half of the year, that is, from April
to September. In the winter months, on the other hand, the source of the
“highs” is different, though they reach the same terminals.




                            HISTORICAL FACTS


                              THERMOMETERS

Galileo discovered the principles of the thermometer in 1592. The Grand
Duke of Tuscany, Ferdinand II, is given credit for perfecting it in
1610. Athanasius Kircher is given credit for the discovery of the
mercurial thermometer. This was about 1641. Ferdinand the II, in 1650 or
thereabouts, filled a glass tube with colored alcohol and hermetically
sealed it after graduating the tube. Fahrenheit is given credit for the
discovery that water freezes always at the same temperature. With these
facts he devised a scale for thermometers in 1714.


                          THERMOMETER RECORDS

A temperature of 111° below zero has been recorded at an altitude of
48,700 feet in the United States.

The highest record in the United States Weather Bureau was taken in
Death Valley, Cal., on June 30, July 1 and 2, 1891, when the thermometer
reached 122° F. Death Valley is also given credit for the highest known
monthly temperature, which was 102° F. in the month of July. Arctic
expeditions have records of 73° and 66° below zero. This is the greatest
natural cold recorded. The average temperature in the United States is
52.4°; the average temperature in England is 50°.

In the interior of Australia a record has been taken of a drop of 60° to
70° in a few hours; whereas the most rapid change recorded in the United
States was 60° F. in twenty-four hours. This record has been made twice,
in 1880 and again in 1890.

The lowest temperature recorded in the United States Weather Bureau was
at Poplar River, Mont., January, 1885, when the thermometer registered
63° below zero.

The estimated heat of the sun is 10,000°; the highest artificial heat
obtained is 7,000°. Regarding the heat of the sun, no definite
conclusions have been arrived at, so the above temperature is only
approximate.


                   REGIONS OF LEAST RELATIVE HUMIDITY

Least relative humidity is found in places southwest of Arizona, where
the average is about 40°. Fifty degrees humidity means half as much
moisture as is necessary for complete saturation. The average in other
parts of the country is from 60° to 80°.

Steel boils at 3500°; water boils at 212°; liquid air submitted to a
degree of cold where it ceases to be a gas and becomes a solid is 312°
below zero. Professor John Dewar of England is credited with some of the
most remarkable experiments with low temperature, and at these
temperatures made some wonderful discoveries. He went down so cold that
he could freeze liquid air back into a solid; he continued further until
he reduced hydrogen, a very light gas, to a liquid. This was at 440°
below zero. One of the most remarkable things he did was to freeze
hydrogen into a solid.

Water boils at 183.2° Fahrenheit on top of Mt. Blanc; water boils at
194° Fahrenheit on top of Mt. Quito.


                               BAROMETERS

Torricelli is given credit for the discovery of the principles of the
barometer. Otto Von Guericke, of Magdeburg, to whom we are indebted for
the air pump, is credited as being the first person to use the barometer
as a weather indicator.

Because of the fact that the mercurial barometer is not adaptable for
portability, many scientists began work on producing a barometer without
fluid that could be easily carried about and would give accurate
results. In 1798 M. Comte, professor of aerostatics in the school at
Meudon near Paris, invented the aneroid barometer, which he used in his
balloon ascents. This instrument has been described fully on page 55.


                           BAROMETER RECORDS

Lowest reading taken in the United States by the United States Weather
Bureau was 28.48, or practically three quarters of a pound per square
inch below normal. Altitude records have been taken with the barometer
as high as 85,270 feet. This record was made at Uccle Observatory,
Belgium, the pressure being 0.67° at this point.


                                  HAIL

Hail varies from one-tenth inch to more than five inches in diameter.

The following is an extract from the “Memoirs of Benvenuto Cellini” of a
terrible hail storm in Lyons, France, in 1544: “The hail at length rose
to the size of lemons. At about half a mile’s distance all the trees
were broken down, and all the cattle were deprived of life; we likewise
found a great many shepherds killed, and we saw hailstones which a man
would have found it a difficult matter to have grasped in both hands.”

New Hampshire has the record for the largest hailstones seen here so
far; they were 4 inches in diameter and weighed 18 ounces, and were 12½
inches in circumferences.


                                RAINFALL

There are records in Japan of where rain has reached 30 inches in
twenty-four hours; in India where it has reached 40 inches in
twenty-four hours.

The average rainfall in the United States is 35 inches.

There are certain places in India where the yearly rainfall averages
over 470 inches; whereas other regions of India show less than 4 inches.

The higher the clouds are in the air, the larger the drops of rain when
they reach the earth.

The heaviest annual rainfall recorded any place in the world is on the
Khasi Hills in Bengal, where it registered 600 inches. The major part of
this was in half of the year.

The greatest amount of rainfall is in the northwestern part of the
United States; the least amount is in Arizona, the southwestern part. In
some parts of Egypt and Arabia, the only moisture that is received there
is in the form of dew.

The average cloudiness of the earth has been estimated between 50 and 55
per cent. This amount slightly exceeds the cloud conditions of the
United States.

Unalaska has a record of extreme cloudiness for one whole month,
February, 1880.

Sir J. C. Ross, an Arctic explorer, recorded a shower of nearly an
hour’s duration on Christmas day, 1839, without a cloud in sight.

A similar record was made on June 30, 1877, at Vevay, Ind., where a
shower lasted for five minutes in a cloudless sky.

A fall of yellow snow was recorded at South Bethlehem, Pa., in 1889.
Examination showed this coloration to be due to the pollen of the pine
trees which had been blown into the atmosphere before the fall.

Another record of yellow rainfall was recorded at Lynchburg on March 21,
1879.

Golden snow was recorded at Peckoloh, Germany, in 1877.

Green and red snows have been observed during Arctic explorations, due
to a minute organism that was in the atmosphere.

When the temperature of the atmosphere is nearly 32° during a snow storm
and the wind is blowing, the flakes being damp and the snowfall heavy,
the flakes are apt to unite to form large masses of snow in the
atmosphere or air, which accounts for some of the following records:

At Chapston, Wales, in January, 1888, the snowflakes measured 3.6 inches
in length and 1.4 inches in breadth, and 1.3 inches in thickness. They
amounted to 2½ cubic inches of water when melted.

There are some remarkable instances of where hailstones have cemented
together, making large masses of ice. Some remarkable records of this
kind have been recorded in India.

In Morganstown, Va., on April 28, 1877, hailstones 2 inches long and 1½
inches in diameter fell.

The mean yearly pressure of the United States ranges between 30 and 30.1
inches when reduced by ordinary methods to sea level.

In Unalaska, January 21, 1879, the barometer reading of 27.70 inches was
recorded, and another low reading was made at Stykkisholm of 27.91
inches on February 1, 1877. On September 27, 1880, a ship on the China
Sea experienced a terrific typhoon, during which the barometer went down
in four hours from 29.64 to 27.04 inches.

The greatest temperature ranges recorded are in the interior of Siberia,
where at Yakutsk they recorded a range of 181.4°.

The most remarkable changes recorded within twenty-four hours have been
at Fort Maginnis, Mont., January 6, 1886, a fall of 56.40°; at Helena,
Mont., January 6, 1886, a fall of 55° in sixteen hours; at Florence,
Ariz., June 26, 1881, 65° rise. On the northern edge of the African
desert the temperature of the air rose to 127.4°.

The lowest single temperature in the world was recorded at Werchojansk,
Siberia, in January, 1885, when it was 90.4° below zero, while the
average temperature for the month at the same place was 63.9° below
zero.

Highest mean rainfall occurs in Sumatra, averaging about 130 inches; the
rainfall of 493.2 inches per year occurs at Cherapunji, Assam, India,
which is the largest in the world.

The lowest rainfall in the world occurs at Southeast California, West
Arizona, and the valley of lower Colorado, where the rainfall averages
less than 3 inches.

The most remarkable rainfall recorded in the United States for
twenty-four hours occurred at Alexandria, La., June 15, 1886, when the
rainfall reached the enormous amount of 21.4 inches. The most remarkable
rainfall recorded in the world occurred at Purneah, Bengal, September
13, 1879, when the rainfall reached the unprecedented amount of 35
inches in twenty-four hours.


                              CLOUDBURSTS

On August 17, 1876, at Fort Sully, Dakota, occurred one of the heaviest
cloudbursts ever known. The water moved out of the canyon on the
opposite side of the Missouri in a solid bank three feet deep and 200
feet wide. There are many other remarkable cloudbursts recorded doing
great injury, drowning and killing many people.


                             WIND VELOCITY

Among the most remarkable wind velocity records is that of Cape Lookout
on October 17, 1879, when the wind blew at a rate of 138 miles an hour.

One of the worst cyclones ever recorded in North America was the flood,
as it is usually termed, at Galveston, Tex. This storm began on the 1st
day of September, 1900, and lasted until the 12th. It reached its
maximum destructive force on the 8th. Six thousand lives were lost and
$30,000,000 worth of property was destroyed.

Even worse than any of these was the one at Calcutta in 1864, followed
by a storm wave over 16 feet high, causing a death-rate of 45,000
persons.


                               BLIZZARDS

The blizzard in Dakota of 1873 is one of the worst on record, but
probably the most disastrous in the United States occurred in Montana,
Dakota, and Texas on January 11, 1888. The loss of life exceeded 100
persons.


                               TORNADOES

The United States is more liable to tornadoes than any other part of the
globe. In the United States over 3,000 people have been killed by
tornadoes and thousands more have been injured. The greatest loss of
lives recorded by tornadoes was at Adams City, Miss., on June 16, 1842,
when 500 lives were lost.

The most remarkable hail storm was that of July 13, 1788, through France
to Belgium, and did a property damage of over five million dollars.

There have been many destructive hailstorms in the United States. One on
July 6, 1878, at central New York extended into parts of Massachusetts,
Rhode Island and Connecticut. Stones fell recorded to measure 7 inches
in diameter.


                        ROTARY MOTIONS OF STORMS

Benjamin Franklin has been given credit for the discovery that storms
have a rotary motion, and that they move from west to east. This
discovery was made in 1747.

Franklin did not positively prove these facts, and it remained for
Redfield, Espy, Maury, Abbe to substantiate the truth of this statement.


                 THE FIRST UNITED STATES WEATHER BUREAU

The first United States Weather Bureau was established in 1870. General
Albert J. Myer was the first chief of the United States Weather Bureau.

It is estimated that we are 250,000 miles from the moon.

At high altitudes, the cover of a kettle must be weighted down in order
to boil an egg hard. This is to enable the pressure of steam to allow
temperature high enough for boiling. In other words, it would be
impossible to boil an egg in an open vessel at a high altitude.

------------------------------------------------------------------------




                               MEMORANDUM




[Illustration]

                             Rain Tomorrow!

You do not like your ball game or picnic postponed just because of rain,
do you? You want a bright day for that event. Then don’t guess what the
weather will be on a certain day—know. Learn to use the

                         Gilbert Weather Bureau

to read weather indications from instruments set up by yourself—in your
own home. This is an outfit you will like immensely. Made specially for
your use and to provide you with a new kind of play.

The fun you get in making records of changes in temperature, in
humidity, and in making forecasts will surely be great. Your boy friends
will listen to you with interest when you explain to them the cause of
storms and how important it is to have a knowledge of climatic
disturbances. The outfits contain all the necessary equipment and a big
book on weather, telling you how to know when it’s going to storm and
many other interesting things. Your dealer will show you the Gilbert
Weather Bureau Sets. If he hasn’t them, write

                       THE A. C. GILBERT COMPANY

               514 Blatchley Avenue      New Haven, Conn.

    In Canada: THE A. C. GILBERT-MENZIES CO., Limited, Toronto, Ont.
   In England: THE A. C. GILBERT CO., 125 High Holborn, London W.C. 1




[Illustration]

                             WHAT IS SOUND?

Do you know that hearing is just feeling with the ear? That in reality,
the thing we call sound, which we think of as a noise or as a musical
note, is just an impression on the brain? Very few boys know this, and
if you would like to be one of the few that do, you surely want an
outfit of

                       Gilbert Sound Experiments

With one of these outfits you can find out just what sound is—how it is
produced—why some pianos sound better than others—why a violin produces
a musical tone, and many other things, including a number of startling
table rapping tricks with which you can astonish your friends. A big
book of instructions tells you how to perform every experiment. Get one
of these outfits today. The best toy dealer in your town should have it;
if not, write us and we’ll tell you where you can get it.

                       THE A. C. GILBERT COMPANY

                514 BLATCHLEY AVE.      NEW HAVEN, CONN.

       In Canada: The A. C. Gilbert-Menzies Co., Limited, Toronto
  In England: The A. C. Gilbert Co., 125 High Holborn, London, W. C. 2




[Illustration]

                              In the Dark!

A knock on the head with a hatchet or a stab with a knife doesn’t sound
pleasant, but you’ll enjoy apparent treatment of this kind and so will
your friends who watch your shadow show. Make your boy friend rise in
the air—change him into a bird or a cat—create freakish images. It’s
easy! And laugh—your audience sure will enjoy it because it’s
new—nothing like it. An entertainment made for boys who want real fun.
But that’s only a few of the many things you can do with

                       GILBERT LIGHT EXPERIMENTS

  One of these outfits will help you to understand a great many facts
  about light. You can perform a number of experiments which explain the
  laws of light. Learn about the movie machine, the telescope and other
  optical instruments. There’s a big book on Light with each set, it’s a
  handy size, just right to put in your pocket.

  From this book and your set you’ll get a knowledge of light that will
  be helpful to you always. It’s great fun too, the kind you like. The
  outfit is complete with prisms, mirrors and all the apparatus you’ll
  need to perform the experiments.

           _Ask your dealer to show you this new Gilbert toy._
                         _If he hasn’t it write_

                       THE A. C. GILBERT COMPANY

               514 Blatchley Ave.,      New Haven, Conn.

    In Canada—The A. C. Gilbert-Menzies Co., Limited, Toronto, Ont.
  In England—The A. C. Gilbert Co., 125 High Holborn, London, W. C. 1




[Illustration: GILBERT BOY ENGINEERING]

            _The Most Helpful Book for Boys Ever Published_

[Illustration]

[Illustration]

Think of it! “Football Strategy,” by Walter Camp—“How to Pole Vault,” by
Former World’s Champion, A. C. Gilbert—“Flying,” by Eddie Rickenbacker,
and “Athletic Training,” by the famous Yale trainer, Johnny Mack.
Chapters about signalling, wireless, wonderful heat, sound and light
experiments, how to build a real weather bureau station of your own,
chemistry for boys, electrical, hydraulic and pneumatic engineering and
surveying, practical carpentry—all in one finely illustrated book. It’s
yours for a quarter and worth dollars to you.

 _The Greatest
 Book for Boys
 in Years_

[Illustration]

 _Buy it from your dealer, or send us 25c today. You’ll never be sorry_


                       The A. C. Gilbert Company

                          514 Blatchley Avenue
                          New Haven : Conn.

------------------------------------------------------------------------




                          TRANSCRIBER’S NOTES


 1. P. 67, changed “it means that there is one one-hundredth of an inch
      of rain” to “it means that there is one one-tenth of an inch of
      rain”. [Makes the math consistent with the rest of the section.]
 2. P. 68, changed “by one hundred for actual rainfall” to “by ten for
      actual rainfall”. [Makes the math consistent with the rest of the
      section.]
 3. Silently corrected obvious typographical errors and variations in
      spelling.
 4. Retained archaic, non-standard, and uncertain spellings as printed.
 5. Enclosed italics font in _underscores_.
 6. Enclosed bold font in =equals=.