I'JiOCEEUlNGS: PlIILOSOl'HK'AL SOCIETY ISo 



f/X (do — dj) 



dAii- V)- + dAV -v)- = 



• TV 



in wliicli V is the velocity of wave propagation, d\ and r/o (ho densities 

 of the layers whose velocities are u and v lespectivejy, q the gravity 

 acceleration, antl X the wave length. If, now, the nnder layer is colder 

 than the upper, as often happens <luring winter, and lather shallow, 100 

 meters to 500 meters thick, say, the passage of the air billows, like the 

 passage of waves in shallow water, necessarily prodnces greater oi- less 

 cori-espomling changes in the pressni'e on the bottom layer changes 

 that appear as a seiies of rii)ples in the I'ecord of a sensitive barograph. 

 Furthermore, such shallow air billows, like shallow water waves, doubt- 

 less are turbulent — a condition that accounts, prcsumabh', for the 

 surprisingly rough flying the aviator often experiences during winter 

 at low levels (300 meters and less). 



During summer when air billows rarely form near the surface, thougii 

 frequently at greater altitudes, especially that of the ciri-us clf)ud, 

 baiometric ripples and shallow turbulences of the kind just mention(>d 

 seldom occur. This, doubtless, is because wave disturbances in air 

 as in water do not penetrate far beneath the wave level. 



Discussion: Mr. Littlehales called attention to the fact that where 

 there are two layers of water of different density, waves frequently 

 occur at the interface that separates the two watGr layers and yet no 

 waves are visible on the surface. These waves at times are sufficient 

 to impede the progress of vessels. The paper was further discussed 

 by Messrs. White, Burgess, Sweet, Buckingham, and Sosmax. 



H. L. Curtis, Recording Secretary. 



