12 BLAIR— EXPLORATION OF THE UPPER AIR [March s. 



International Commission for Scientific Aeronautics, using either 

 kites or sounding balloons, or both. Captive and manned free bal- 

 loons are occasionally used. Of these observatories, the universities 

 of Manchester and Kasan each maintain one. 



Apparatus and Methods. 



The site chosen for an upper air observatory is to some extent 

 determined by the kind of work to be done. A kite field should be 

 clear of trees and other obstructions that might either entangle the 

 wire or hinder the movements of the men who manipulate the kites. 

 It should be situated on an eminence just high enough to prevent its 

 being sheltered by any other in the immediate vicinity, but not high 

 enough to introduce the complications of mountain and valley 

 efifects, unless indeed such local effects and not the general condi- 

 tions obtaining in storms as they pass, be the object of the study. 

 It is well if the country for thirty miles around in the vicinity of 

 the field be free from large bodies of water and inhabited, for kites 

 break away at times and these conditions facilitate their return. 

 Close proximity to a city, on the other hand, is likely to bring kite 

 flyers into unpleasant relationships with the local telephone and 

 other electric companies who transmit power on overhead wires. 



For captive balloons the conditions should be the same as for 

 kites. Sounding balloons may be started from any place at which 

 the true surface conditions can be recorded for comparison with 

 the upper air data, except that the land area immediately to the 

 east should be free from large lakes and fairly well settled. The 

 balloons set free in this country by Professor Rotch have invar- 

 iably traveled in an easterly direction and landed within a radius 

 of 300 miles from their starting point. Each balloon carries with 

 it instructions to its finder for packing and shipping and informs 

 him that he will be rewarded for his trouble. This plan has brought 

 back about 95 per cent, of all sounding balloons liberated in St. 

 Louis, the only place in our country so far chosen for this work. 



The ideal upper air observatory is one at which all three of 

 these methods may be used, kites and captive balloons being less 

 expensive and more efficient for levels up to 3,000 or 4,000 meters, 

 2 or 3 miles, and sounding balloons for higher levels. 



