5o 



TEE POPULAR SCIENCE MONTHLY 



HOLES IN THE AIR 



By W. J. HUMPHREYS, Ph.D. 



PROFESSOR OF METEOROLOGICAL PHYSICS, U. S. WEATHER BUREAU, WASHINGTON, D. C. 



THE bucking and balking, the rearing, plunging and other evidences 

 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 air " is brief and elegantly expres- 

 sive of the fact that occasionally at various places in the atmosphere 

 there are conditions which, so far as flying is concerned, are mighty 

 like unto 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. 



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

 a place devoid of air and of all pressure. The surrounding air would 

 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 



