PROCEEDINGS OF THE ACADEMY AND AFFILIATED 



SOCIETIES 



GEOLOGICAL SOCIETY OF WASHINGTON 



The 257th meeting was held in the Cosmos Club April 24, 1912, Vice- 

 President White in the chair. The following informal communications 

 were presented: 



Relation of the Sewanee conglomerate to the Bon Air sandstone: Charles 

 Butts. 



A zircon rock from Virginia: F. L. Hess. 



Koenigsberger on geothermic gradients and -petroleum: E. W. Shaw. 

 Mr. Shaw reviewed a paper by Professor Koenigsberger which treats 

 of the technique of measuring underground temperatures, of the temper- 

 ature gradients in numerous borings, mines and tunnels for which data 

 are given, and of the conclusions that may be drawn therefrom. In 

 the computation of the gradients in mines and tunnels the observed 

 temperatures are corrected for the effect of forced ventilation, water 

 evaporation and movement, the shape of the surface and other factors 

 which must be considered in working out the isogeotherms. Professor 

 Koenigsberger also takes into account the difference in heat conductivity 

 of different rocks, ojr of the same rocks in different directions with refer- 

 ence to the cleavage, and the effect of water in the rocks of nearby large 

 bodies of water on the surface. He considers the age of the strata, their 

 attitude, their degree of metamorphism, the presence or absence of 

 evidence of vulcanism, the heat generated by the oxidation of iron sul- 

 fide and hydrocarbons, the hydration of anhydrite and other minerals, 

 the depolymerization of bituminous substances, especially coal and oil, 

 and, finally, radioactivity. After evaluating all these factors, he arrives 

 at the conclusion that whereas the average rate of increase in temperature 

 within the earth is about 1°C. for 30 m., in coal regions there is a higher 

 gradient, in oil and gas fields still higher, and that this fact can be used 

 in prospecting. 



Professor Koenigsberger's observations seem to have been made with 

 care and precaution, but there appear to be weak points. (1) The data 

 from mines and tunnels are subject to so much correction for circulating 

 air and water, and the arrangement of mountains and valleys at the 

 surface, etc., that one hesitates to put much weight on them, especially 

 as slight error would make a great difference in the conclusion. (2) Of 

 the fifty or sixty measurements in excavations of all lands, only a few 

 were made by the author himself and none was made with instruments 

 more accurate than the best maximum mercury thermometer, which is 



393 



