Chapter II: Part 2

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.

_Courtesy Julien Friez & Sons, Baltimore, Md._

Fig. 34
]

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.

_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.

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.

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.

_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.

Fig. 40
]

_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.

_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.

_Courtesy Julien Friez & Sons, Baltimore, Md._

Fig. 43
]

_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.

_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.

_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
─────┴───┴───┴───┴───┴───┴───┴───┴───┴───┴────┴────┴────┴────┴────┴────┴────┴────

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

Fig. 47

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

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.

_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.

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.

_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.

Fig. 52
]

Fig. 53
]

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