THERMAL CONDUCTIVITIES OF ROCKS 269 



and Zobel's application to physical geology of the mathematical theory of 

 heat conduction in homogeneous media, and calculation by them of a 

 number of curves for the cooling of lavas and laccoliths. Ehrenburg 

 continues : 



' Unfortunately, their results are based on the narrowing assumption that 

 the thermal constants of the cooling mass are identical with the constants 

 of the underlying or surrounding rock. However, the shape of a cooling 

 curve depends not only upon the configuration of the bodies between which 

 the heat transfer occurs and their initial temperature difference, but also 

 upon the relative values of conductivity, density and specific heat. The 

 writer believes that the difference in thermal constants is an important 

 factor in modifying the character of a temperature curve ; and in this 

 paper is proposed a new method of treating the flow of heat in two hetero- 

 geneous solids in contact, and also is demonstrated its application to several 

 particular cases similar to those treated by Ingersoll and Zobel.' 



Rate of Temperature Change. 



(Editorial Note.) 



The Oil and Gas Journal, Tulsa, vol. 31, no. 3, 1932, p. 109. 



In this article temperature gradients for a series of measurements are 

 enumerated. In certain wells in Pennsylvania the temperature gradient 

 indicated an increase of 1° F. for each 58 to 64 ft. of depth, and in California 

 an increase of 1° for each 52 ft. is often observed. Other temperature 

 investigations show that in some districts the temperature rises at an even 

 faster rate, often at i° for each 40 ft. 



In the Salt Creek field in Wyoming well temperatures at a depth of 100 ft. 

 ranged from 51 -4° to 65 -27° F., and at 2,000 ft. they ran from 79 to 98-4°. 

 Temperature measurements in a well in the Teapot Dome field, Wyoming, 

 showed 71-6° at 1,000 ft. and 125° at 2,867 ft. In another well in the same 

 field the temperature at 25 ft. was found to be 76 , but at 2,790 ft. it was 

 124-5°. A completely dry well in the Teapot Dome field showed a tempera- 

 ture of 52° at 100 ft. and of ioi° at 2,000 ft. In wells in California the 

 temperature at 4,000 ft. varied between 150° and 170°. A thermometer 

 run to the bottom of a well 4,050 ft. deep in the Wellington-Fort Collins 

 area of Colorado recorded 157°. This was 3 higher than that registered by 

 a well 7,900 ft. deep near Kane, Pa. 



Temperature measurements made by E. M. Hawtoff, of the Bureau of 

 Economic Geology, in a well in the Big Lake field in Reagan County, Tex., 

 showed the following temperatures at depths below 5,000 ft. : At 5,700 ft., 

 122° F. ; 6,500 ft., 135° ; 7,000 ft., 152° ; 8,000 ft., 161° ; 8,300 ft., 170°. 



Temperature of Formation of an Epi-thermal Ore Deposit. 



By H. C. Boydell. 



Bulletin of the Institution of Mining and Metallurgy, London, nos. 331 and 

 332, 1932, pp. 1-43 and 25-39. 



This paper was presented at the seventh ordinary general meeting of the 

 forty-first session of the Institution, held on April 21, 1932. In this article 

 a discussion of the paper is given. 



The present paper provided a striking example of a problem in mining 



