114 PROCEEDINGS OF THE AMERICAN ACADEMY, 



sure and temperature. There can be no doubt that at high pressures 

 there are other than kinetic effects involved at least in pressure. 



It is a pleasure to acknowledge generous assistance from the Rum- 

 ford Fund of the American Academy of Arts and Sciences for the 

 purchase of apparatus and supplies, and from the Bache Fund of 

 the National Academy for an assistant in some of the experimental 

 work. 



Jefferson Physical Laboratory, 

 Harvard University, Cambridge, Mass. 



