The Science Notebook
Gilbert Weather Bureau - Part II

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NOTE:  This book was published around 1920 as a manual to accompany the Gilbert Weather Bureau sets.  The sets and manual were part of the "Boy Engineering" series, While some of the experiments and activities here may be safely done as written, some of them may be considered hazardous in today's world, such as handling a mercury barometer.  In addition, some of the information contained in this book is either outdated or inaccurate.  Therefore, this book is probably best appreciated for its historical value rather than as a source for current information and good experiments.  If you try anything here, please understand that you do so at your own risk.  See our Terms of Use.

Pages 22 - 43


NOTE:  Many figures have been relocated from their position in the printed text to make them more readable on a web page.  This may or may not be indicated in the text.

   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.


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


Wind blowing at 20 miles per hour has a force of 1 1/4 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.


[Originally contained Figs. 18-23]


[Originally contained Figs. 19A-23A]



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

Light Air
Light breeze (or wind)
Gentle breeze (or wind)
Moderate breeze (or wind)
Fresh breeze (or wind)
Strong breeze (or wind)
Moderate gale
Fresh gale
Strong gale
Whole gale
From 0 to 3
Over 3 to 8
 "   8  " 13
 "   13 " 18
 "   18 " 23
 "   23 " 28
 "   28 " 34
 "   34 " 40
 "   40 " 48
 "   48 " 56
 "   56 " 65
 "   65 " 75
 "   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:

[Color added]

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 stationery. 

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

[Color added]

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.

[Color added]

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 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. 

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. 23A), indicates the approach of a tropical hurricane, or one of the extremely severe and dangerous storms which occasionally move across the Great Lakes and Atlantic Coast. 

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 instru-


ments and the method of recording the indications will give you an insight into how the various government weather stations arrive at their forecasts.

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.  Our 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 pan that records the rainfall also records the number


of hours of sunshine 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. 


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. 

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 data great elevation.  Its formation is fibrous and it is particularly characterized for its many varieties of shapes.  It also has of 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 com 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:

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 called the "mackeral" sky. 

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

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. 


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


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 a 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's center, it turns to the right in the form of a whirlwind, spirally, moves around the storm's center.  (See Fig. 31.)  It is this whirling process that has given it the named, 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.

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 movements 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.



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 falling temperature followed by clear weather, rising barometer, decreasing humidity and falling temperature in the western quadrants. 

Buys Ballots' 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. 


In speaking of low-pressure storms we call them storms 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 storms centers. 

The Buys Ballots' 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 is 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. 


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 the 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 have no doubt 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.


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 at them as being very severe, are very often mild and not of an intensive character.


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 iis 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 the facilities for doing it, it is well to see it performed in any physics laboratory.

Immediately 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 effects 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.


Water vapor is always present in the air.



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.


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 water 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 19.78 grains of vapor; at 80 F., 10.95 grains; at 50 F., 4.09 grains, and at 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 snowflakes. 

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


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 obser-  


vation 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 led certain men to gain quite a reputation for prophesying what the weather is going to be. 


Various appearances that come from 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 or 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. 


When high clouds are seen crossing the sun or the moon in a different direction from the lower clouds, this indicates a 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 like 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 grows into cloudiness, this indicates rain. 


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. 


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 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.)


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 set 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. 

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. 


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.

Go to Part III or To the A.C. Gilbert Collection

 "The Science Notebook"  Copyright 2008-2017 - Norman Young