R-cm -2~ 5/15/31 



Ceiling balloon observations are rather recent developments for practical 

 use when clouds are low. On the average, those balloons are watclne d until about 

 a half mile up. The record ceiling balloon observation in this country is two 

 ailes up. 



But suopose there are no clouds? How are you going to tell about the 

 speed and dii*ection of the wind when there are no clouds? and at the levels 

 where there are no clouds? 



The so-called "pilot" balloon observ;\tions take care of that. In those 

 observations, \7ind direction and velocity is determined by watching sn:all 

 balloons through telescopic instruments r.uch like a surveyor's transit. The 

 balloons are inflated to a certain size and lift as determined by "weighing" 

 on special scales. Barring leaks, it is known fron tests that those balloons 

 will rise at a certain even rate, per r.inute. By keeping the instrument sighted 

 on the balloon and reading the angles from minute to ninute, our surveyors-of- 

 the-wind ,^et the data needed to find the horizontal speed at which the balloon 

 and wind which carries it move. 



On the average, pilot balloons get the wind facts up to three niles high. 

 In unusually clear air, the powerfiil little magnifying instruments have followed 

 them a horizontal distance of UO r.iles* The record height reached by a pilot 

 baloon in the United States is about 21 riles- The world's record is 2k r.iles 

 up. 



All very well for the wind, you say? How about the temperature and 



humidity way up there? 



Well, our weather nen get those records too. 



To do it, they use sounding balloons, which are about twice the diar.oter 

 of the pilot belloons. The sounding balloons carry automatic devices for writing 

 a record of the te.r.perature and humidity, and pressure of the air through which 

 the balloon passes. 



Mr. Sar..uels showed me one of those clever little instruinents . I wished 

 you all could see it. The contr?ction and expansion of a little piece of metal 

 attached to a pen draws the record of the ter.perature. The humidity record is 

 made by a few human hairs which stretch or shrink a wee bit according to the 

 moist-ure in the air. In so doing, they move another pen. The paper wound on a 

 cylinder moves slowly p^st the pens by means of clock-work. 



Mr. Sav-.uels says the avera.^e height reached by soiinding balloons is nine 

 miles. The world's record is 22 miles. That's rather high, and awful cold. At 

 around I30 degrees below zero, any ink would freeze, so smoked paper is used to t- 

 the tracings, which show the ups and down of te -perature and moist-ore in the air. 



Those sounding balloons ex^oand as they rise and finally burst. The records 

 are brought down by parachute. Th;^t is one of the best ways of getting records 

 of extreme heights. One trouble with it is in recovering the instruments and 

 records; especially in rough country. 



In order to get similar records for practical every-day knowledge of the 



