82 



THE NATIONAL GEOGRAPHIC MAGAZINE 



Photograph from Collegiate Balloon School 

 READY FOR A "SOEO" FLIGHT 



This type of observation balloon has one serious disadvantage : 

 when held captive it oscillates in the slightest breeze, making it diffi- 

 cult for the observer in the car or basket to take accurate note of 

 enemy movements and day-to-day changes in fortified positions back 

 of the front-line trenches. 



Jennings self -record- 

 ing color-sense tester 

 probably appears only 

 a little unusual, for it 



is realized that per- 

 fect vision is essential 

 to observation work 



from the clouds, and 

 that any defect of 

 vision might prove fa- 

 tal in a sudden emer- 

 gency. 



The balance test, 

 however, will prove a 

 distinct surprise, for 

 few people realize that 

 the sense of balance is 

 controlled by a fluid 

 which flows back and 

 forth in the labyrinth 

 of the inner ear, just 

 as the fluid in a spirit- 

 level flows back and 

 forth. To set this 

 fluid in motion and 

 see how quickly it re- 

 acts, the candidate is 

 seated in a revolving 

 chair which is spun 

 rapidly around. When 

 it is brought to a stop, 

 the candidate is asked 

 to point out certain 

 objects, his visual dis- 

 turbance is noted, and 

 a pretty good estimate 

 is made as to whether 

 he could bring him- 

 self out of a spiral or 

 right his machine af- 

 ter a falling-leaf evo- 

 lution. 



are, of course, fundamental. The pro- 

 spective avatior is probably not surprised 

 when his chest is tapped by the medical 

 examiner, when he is asked to expand 

 his lungs, and when his arm is bound in 

 a tight rubber band to test his blood pres- 

 sure. Similarly, the testing of the nose 

 and throat to guard against any obstruc- 

 tion in ventilation which might cause ver- 

 tigo or nausea may be unexpected, but 

 not startling, to a man who expects to go 

 through the aviator's wide range of tem- 

 perature and atmospheric pressure. The 



THE MENTAL EXAMINATION IS NOT 

 FORMIDABLE 



Next comes the mental examination, 

 not nearly so formidable as the phrase 

 implies. Its purpose is to find out from 

 the candidate's records, from his history, 

 education, athletic ability, and general 

 presence whether he has the alertness, 

 aggressiveness, accuracy, and sense of 

 responsibility desired. A good aviator 

 should be neither all brains and no phy- 

 sique nor all physique and no brains, but 



