Wright and Lar sen — Quartz as a Geologic Thermometer. 447 



below 575°, while graphic and granite pegmatites and granites 

 and porphyry quartzes were in all probability formed above 

 575°. With the quartzes thus examined were associated other 

 minerals, the order of precipitation of which relative to that of 

 the quartz could be determined in certain instances and thus 

 temperature limits for the formation of these in turn ascer- 

 tained. 



The writers desire to express their indebtedness to Dr. A. L. 

 Day for the precise thermoelectric measurements noted in the 

 foregoing pages ; to Dr. W. P. White for data on the specific 

 and latent heats of quartz ; and to Messrs. A. C. Spencer, E. S. 

 Bastin, Arthur Keith, A. Knopf, Charles W. Wright, of the 

 IT. S. Geological Survey, and Professor G-. P. Merrill of the 

 National Museum, for specimens of quartz from the localities 

 cited in the descriptions above. 



Geophysical Laboratory, 

 Carnegie Institution, 



Washington, D. C. 

 March 4. 1909. 



