GEOPHYSICAL INVESTIGATIONS SUGGESTED 



In the interests of the Science of Petrology several of us, who have 

 devoted much of our time and energies to petrological matters, call 

 attention to a statement of some of the problems in the line of physico- 

 chemical investigation which could be undertaken in a properly 

 equipped laboratory and urge the importance of laying the matter 

 before the geological committee of the Carnegie Institution in order 

 that it may be favorably inclined toward the investigations proposed, 

 some of which are already being carried on under the patronage of 

 the Carnegie Institution. 



It will be noted that many of them are of far-reaching importance 

 to the advancement of general geological problems, of which the 

 knowledge of the properties and history of rocks forms a very con- 

 siderable part, the problems connected with rocks affecting the whole 

 geological system. It therefore happens that problems stated in this 

 connection may naturally be restated in others. 



INVESTIGATION OF IGNEOUS ROCKS. 



I. Determination of Changes of Condition Accompanying 



Changes of Temperature. 



A. With normal atmospheric pressure. 



i. Change of volume and of viscosity ; that is, the rigidity, 

 melting point, and liquidity of — 



(a) Rock glasses of known chemical composition, 



corresponding to known igneous rocks. 



(b) Glasses of single minerals. 



(c) Crystals of single minerals. 



This involves fusion in open crucibles with the determination of 

 temperature thermo-electrically by methods employed by Dr. Barus 

 and Dr. Day in the laboratory of the U. S. Geological Survey. 



B. With high pressures in closed vessels. 



The effect of increasing pressure on the volume and the vis- 

 cosity — rigidity, melting point, liquidity — of rock glasses, 

 and glasses and crystals of known minerals. 



(i95) 



