154 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1936 



EXPLORING THE UPPER ATMOSPHERE 



Today there are eight different ways of obtaining information 

 about the nature and properties of the upper air (fig. 2). 



Pilot balloons filled with hydrogen can carry up small, light, 

 ingenious recording devices. If the balloon is recovered on its 



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 Region 



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 Reqion 



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Figure 2. — The atmosphere. The diagram indicates the heights of mountains, Plccard's 

 gondola balloon, sounding balloons, the ozone region, meteors, northern lights, and the 

 two main regions (E and F) capable of reflecting radio waves. (From Physics, by 

 A. S. Eve. Thornton Butterworth, Ltd., London.) 



return to earth, there are records of elevation, temperature, and 

 humidity. Such balloons may also be followed with a transit instru- 

 ment, or theodolite, so that the wind velocity at different levels may 

 be deduced. The greatest elevation attained by a balloon without 



