488 Mr. J. P. Joule and Prof. Thomson on the Thermal Effects 

 Series 1. 



D 



* The true value of — - for any particular temperature would be the 



depression of temperature that would be experienced by air approaching 

 the narrow passage at that temperature and under ten atmospheres of pres- 

 sure, since P is measured in atmospheres, and the common logarithm is taken. 



