6 Strom EYI:r, Tlic Fowiatioii of Minci-ais hi Granite. 



ence of 9.';'-" between the melting temperature of the two 

 substances at a pressure of one atmosphere, there is no 

 difference at about 750 atmospheres, and the difference 

 would evidently have been reversed to about lo'^C, if the 

 experiments could have been extended to a pressure of 

 1,800 atmosjjheres. 



70 



100 '200 '500 1400 1500 '600 '700 '800 '900 



Now, taking the mean densit}- of the earth's crust at 3, 

 a depth of 10 feet is equal to a pressure of about one 

 atmosphere, so that at a depth of 18,000 feet, if one could 

 keep the temperature below about qo^C, one would find 

 that napthylamine melts first b)- about lo'^'C , while on 

 the surface it nielts last b}'9^'-^C. \\'ith the one substance 

 the rate of increase of melting temperature is about I*"'C. 



