HOLES IN THE AIR. 



By \Y. J. Humphreys, Ph. D., 

 Professor of Meteorological Phymcs, United Stafcs Weather Bureau, Washington, D. C. 



[With 3 plates.] 



The bucking and balking, the rearing, phmging, and other evi- 

 dences of the mulish nature of the modern Pegasus soon inspired 

 aerial jockeys to invent picturesque terms descriptive of their steeds 

 and of the conditions under which their laurels were won or lost. 

 One of the best of these expressions, one that is very generally used and 

 seems to be a permanent acquisition, is " holes in the air. " There are, 

 of course, no holes in the ordinary sense of the term in the atmosphere — 

 no vacuous regions — but the phrase ''holes in the aii'" is brief and 

 elegantly expressive of the fact that occasionally at various places in 

 the atmosphere there are conditions which, so far as flying is con- 

 cerned, are mighty Hke imto holes. Such conditions are indeed real, 

 and it is the purpose of this paper to point out what some of them 

 are, when and where they are most likely to occur, and how best to 

 avoid them. 



wSupposc for a moment that there was a big hole in the atmosphere, 

 a place devoid of air and of all pressure. The surrounding au* w^ould 

 rush in to fill this space with the velocity pertaining to free particles 

 of the atmosphere at the prevailing temperature; that is to say, at 

 the velocity of sound in air at the same temperature, and therefore 

 at ordinary temperatures of about 1,100 feet per second, or 750 miles 

 per hour. Even, therefore, if such a hole existed, it woidd be impos- 

 sible for an aeronaut to get into it — ^he could not catch up with it. 



But, according to the claims of some, if there arc no com]>lete 

 holes in the atm()S])here there are, at any rate, i)laces where the den- 

 sity is much less than that of the surrounding air; so much less 

 indeed that when an aeroplane runs into one of them it drops quite 

 as though it was in a place devoid of all air and without support of 

 any kind. 



This, too, like the actual hole, is a pure fiction that has no support 

 in barometric records. Indeed, such a condition, as every scientific 

 man knows, could be established and maintained only by a gyration 



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