mechanical equivalent of heat 42,683-7 



282 McAdie — Neio Units in Aero-physics. 



Cp equals specific heat of air, equals 9,804,000 



C, " " " '' " 6,971,750 



C 

 k " j^- " 1-4062486 



A " heat equivalent of work " -0000002389 

 1 



A 



H^ " height of convective surface 



T^ " temperature at H„ 



P " specific weight of air -00129305 



P„ " " " " water vapor -00080427 



Note (added August 10, 1910). 



Through the courtesy of Professor Charles F. Marvin and 

 Mr. C. F. Talman, Librarian of the Weather Bureau, the 

 following references have been found, proposing the use of 

 C. G. S. units in measuring atmospheric pressure : 



B. A. A. S. 1888 meeting, page 28. A committee of the 

 British Association proposed the use of the Barad, pressure 

 of one megadyne per square centimeter. 



Monthly Weather Review, vol. xxvi, 1898, page 314, Cleve- 

 land Abbe discusses measurement of pressure in standard units 

 of force. 



C. E. Guillaume proposed to International Congress of 

 Physicists in 1900, use of megadyne under the name Barye; 

 and this was favorably reported by a committee of the 

 Congress. (Travaux, Congr. Int. Phys., Paris, 1900, t. iv, pp. 

 61-62.) 



Sandstrom and Helland-Hansen in their report on Marine 

 Investigation, dated 1902, used the megadyne and the unit of 

 atmospheric pressure and also for hydrostatic pressure. 



Bjerknes and Sandstrom, in 1906, used the unit har as 

 mentioned by Koppen, Quar. Journ. Roy. Met. Soc, April, 

 1909. 



During the present year Koppen, Shaw, Gold, Harwood, 

 Dines and others used the bar. 



