ABSTRACTS OF PAPERS 145 



When pressure on a liquid or solid is released in a certain way, namely, by 

 extrusion through a small orifice, the temperature is raised very considerably. 

 Thus, ordinary rock material, if extruded from a pressure corresponding to a 

 depth of 20 kilometers, would heat itself up nearly 200 degrees centigrade 

 above its original temperature. Moreover, the process may accelerate itself 

 and it may be intermittent in character. This kind of a process would seem 

 to account for certain types of volcanic activity without postulating a liquid 

 reservoir. 



Read from manuscript by H. S. Washington in the absence of the 

 author. 



The preceding four papers were then discussed by James F. Kemp, 

 IT. F. Reid, and A. L. Day. 



Discussion 



Professor Kemp : The speaker referred to the question of the composition 

 of the explosive gases described by Dr. Day and asked if further details of 

 their composition could be given. Speaking of the low temperature, he asked 

 if any such effect was produced in the expansion on emission as is met in the 

 use of compressed air. When the compressed air escapes from an engine or 

 rock drill, there is a great lowering of temperature on expansion, sometimes 

 enough to condense and freeze ally water vapor in the air, if the expansion is 

 not adjusted to allow for it. 



Dr. Day: (In reply to Dr. Reid.) To account for the very superficial com- 

 bustion of dead leaves and dried twigs on the hillside facing the mountain, it 

 does not seem to me to be necessary to invoke any other agency than the 

 momentary increase in the time of exposure to the hot blast caused by the 

 momentary interference of the opposing hill to its passage. 



(In reply to Dr. Kemp.) I am sorry that in closing my address so hastily 

 I omitted to state my conclusion regarding the composition of the blast. In 

 my opinion, it consisted of ash-laden steam with practically no accompaniment 

 of the usual chemically active gases, such as HC1, H,S, S0 2 , and the like. 



USE OF FORAMINIFERA IN DETERMINING UNDERGROUND STRUCTURE. 

 ESPECIALLY IN PETROLEUM MINING 



BY J. A. CUSHMAN 



(Abstract) 



In Tertiary and Cretaceous formations of marine origin foraminifera are 

 usually present and often abundant. .An intensive study of the foraminiferal 

 faunas of these formations in the American Gulf Coastal Plain and other re- 

 gions bordering on the Gulf of Mexico and the Caribbean has shown that the 

 faunas of the various members of these formations are easily recognizable. 

 On account of the small size, most of the foraminifera escape injury in drilling 

 operations. For this reason and from their abundance (sometimes as many 

 as one hundred species in a cubic inch of material), they are of more impor- 

 tance in determining the strata penetrated by the drill than any other group 

 of organisms. When well logs can be examined it is possible to determine 

 X— Bull. Gkol. Soc. A.m., Vol. 33, 1921 



