THE OCEAN OF AIR 



depth is determined by records obtained from small 

 balloons carrying measuring instruments which have 

 risen to this height. As one ascends from the earth 

 toward the top of this vast ocean, the air becomes 

 less and less dense because the higher one goes, the 

 fewer are the layers of air above to press down. If you 

 were to pile up books to a height of two feet, a book 

 near the middle of the stack would be under less pres- 

 sure than those at the bottom, because there are fewer 

 books above it. 



Man has explored this ocean of air in which we 

 live to a height of about eight miles in airplanes and 

 higher in balloons. Study the diagram (Fig. 6) and 

 learn as much as you can about the depth of this air 

 ocean. 



Some scientists believe it to be fifty miles in depth 

 and others as much as two hundred miles. Nearly 

 every year attempts are made to establish new altitude 

 records in airplanes and balloons. This is hazardous 

 inasmuch as the upper atmosphere is very cold and 

 the men who fly the planes and balloons must carry 

 oxygen to breathe, because there is not sufficient of 

 this important gas to keep them alive at the great 

 heights attained. In seeking altitude records the 

 planes and balloons must carry sealed instruments 

 which record the height reached and which are later 

 tested by government scientists. 



Man has explored the 

 stratosphere. Since the 

 historic flight of Dr. Pic- 

 card in 1931 the word 

 stratosphere has become 

 a part of the vocabulary 

 of almost every boy and 

 girl in the country. Do 

 you really know what 

 the stratosphere is? Do 

 you know of what im- 

 portance it is and why 

 men risk their lives in at- 

 tempting to explore this 

 region ? 



Scientists have long 

 recognized that two 

 great layers of air lie 

 above our earth. To the 

 layer which lies next to 

 the earth they have given 

 the name of troposphere 

 and to the one above it 

 the name stratosphere. 

 The troposphere is the 

 one with which we are 



Paul's Photos most familiar. It is be- 



FIG. 7. STRATOSPHERE BALLOON lieved to be about twelve 



miles deep at the equator and about four miles at 

 the poles. The troposphere contains clouds, dust 

 particles, and many tiny living plants known as bac- 

 teria. Its temperature is not constant, varying from 

 commonly known earth temperatures to as low as 

 67 degrees below zero centigrade. 



Next above the troposphere and surrounding it is 

 the stratosphere. There are no clouds in the strato- 

 sphere, and it is believed that the temperature is con- 

 stant at about 67 degrees below zero centigrade. 



Exploration of the stratosphere was first made by 

 Professor Auguste Piccard in May, 1931. With an 

 assistant he rose about ten miles above the earth. 

 Since that time Professor Piccard has made a second 

 ascent, and several others have reached greater 

 heights. In November, 1935, the Americans Stevens 

 and Anderson made a record ascent from Rapid City, 

 South Dakota, reaching an unofficial height of about 

 73,000 feet. 



All of the stratosphere fliers have used equipment 

 similar to that used first by Piccard. A large, partly 

 inflated balloon is attached to a sealed metal sphere 

 below it, in which the observers and their equipment 

 are carried. Observations are made through windows 

 in the sphere. It is necessary to seal the sphere be- 

 cause there is not a sufficient supply of oxygen in 

 the stratosphere to sustain life. The observers must 

 take tanks of oxygen aloft with them as well as cer- 

 tain chemical substances to absorb the carbon dioxide 

 which they continually exhale into the air of their 

 tiny laboratory. 



The great depth of the atmosphere, made up as it 

 is of layers of air, causes the one nearest the earth to 

 be pressed down by the weight of all those above it. 

 Your experiment with the football bladder taught you 

 that even the amount of air that you put in this 

 small space has weight enough to show on the bal- 

 ance. The air over a floor thirty feet square pushes 

 down on the floor with a force of more than nine hun- 

 dred tons. Just think of that ! It hardly seems possible 

 that this gaseous stuff which we call air and which 

 is so light that we do not notice its presence, could 

 possibly weigh so much. 



"The pressure of the air" is a common expression, 

 but many do not understand what it really means. 

 When we say that the pressure of air is fifteen pounds 

 per square inch, we mean that if a column of air as 

 deep as the atmosphere and one square inch in cross- 

 section area could be separated, it would weigh fifteen 

 pounds. In other words, on every square inch of sur- 

 face at sea level air presses fifteen pounds. Of course, 

 as one goes above sea level, up mountains and higher 

 in airplanes and balloons, this pressure gradually de- 

 creases. Air pressures at different altitudes are given 

 in the following tabulation: 



