The Science Notebook
Gilbert Weather Bureau - Part I 

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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  In addition, some of the information contained in this book is either outdated or inaccurate.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.

Cover - Page 21

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

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 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 percent 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 learned about the air. 


If you were 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."


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.

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 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, angry 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 lived in an 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. 


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. 


[Originally contained Figs. 3 & 4.]


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


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 intverted, the contents do not leave the glass.  (See Fig. 4.)


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. 


Take in 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 be 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 on atmospheric pressure.  Guericke is distinguished by his original discoveries of the properties of the air.  He was born at Madgeburg 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 Madgeburg.  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 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. 

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 anemoscope.  He was interested also in astronomy. 


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 eyedropper, 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 on 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 learned what causes these changes in the pressure of the air. 


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.   


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 its swings freely in the air.  (See Fig. 8.) Under this put a little alcohol lamp, or put it over a gas jet or radiator. 


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


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.)


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.  The

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 a 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. 


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 the results that you get now.  The smoke will spread out over a large area. 


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 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. 



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 percent 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 the 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 and our homes, 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? 


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 the fog will never form when it is dry. 


After rain drops have been formed and they freeze in their passage through the air, they become hail-stones. 


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 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 a large masses of snow.  Generally speaking, ten inches of snow makes one inch of rain. 


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. 



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. 


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 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 electricity 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 call thunder.  Often we see several flashes of lightning and 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 defused 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 report is about twelve seconds.  The longest interval is seventy-two seconds and the shortest one second.  Prolonged peels 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. 



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; it's diameter sometimes reaching several hundred feet, being larger above than below, the winds themselves covering a greater space. 

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, 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 in near the surface of the earth for its supply, and this inrush of air 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.  


You will recall in 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, 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[e], 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. 


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 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 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 defuses 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.  


   Moutain 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. 

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

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