558 



PROCEEDINGS OF THE AMEEICAN ACADEMY. 



cause of the close approach of its equilibrium curve with water to a 

 maximum. In general, the internal energy increases on passing from 

 a solid stable at low pressures to the solid stable at higher pressures, 

 but III-II is an exception. The most interesting features found for 

 the equilibrium solid-solid are the probable passing of the I-II curve 

 through the absolute zero, the enormous increase in reaction velocity 

 on approaching a triple point, and the existence in one crystalline form 

 of nuclei about which crystallization to another form may begin. 



Acknowledgment is here made of several liberal appropriations from 

 the Rumford Fund of the American Academy of Arts and Sciences, 

 with which the expenses of this investigation were partially defrayed. 



Jefferson Physical Laboratory, 

 Harvard University, Cambridge, Mass., 

 October, 1912. 



