268 REPORTS ON THE STATE OF SCIENCE, ETC. 



wire and tripod, steel thermometer tubes, and a set of maximum thermo- 

 meters. The distribution of the temperature was investigated in five drill 

 holes. Two of these holes belonged to the region of the future ' shaft ioo,' 

 where mining will take place at a depth of 1,200 m. (4,000 ft.) ; thus it 

 was very important to determine the temperature in advance. The in- 

 fluence of the water in the hole on the normal distribution of the temperature 

 was determined by preliminary observations in two drill holes : the gradient 

 of temperature did not exceed 0-39° C./m.in the first hole and 0-26° C./m.in 

 the second hole. The temperature curves deviated very little from a straight 

 line ; these anomalies could be explained by the influence of water layers, 

 thermal conductivity, convection currents, etc. 



The importance of the analysis of the temperature curve in geothermic 

 investigations is very great ; therefore it is imperative to determine the 

 thermal conductivity of the rock samples in addition to the thermometric 

 observations. 



Recent Geothermal Measurements in the Michigan Copper District. 



By James Fischer, L. R. Ingersoll and Harry Vivian. 



The American Institute of Mining and Metallurgical Engineers, New York, 

 Technical Publication No. 481, 1932, 11 pp. 



Considerations of heat conduction guided the measurements made to 

 determine the actual virgin temperatures at the ' temperature stations.' 

 Holes in which were inserted one or more thermometers were drilled a 

 few inches back from the breast. Mercury-in-glass thermometers were 

 chosen, mainly because of their simplicity and reliability. Two, and. 

 sometimes three, thermometers were inserted in these holes, and were 

 read at 2-hour intervals until three or four readings had been taken. This 

 proceeding was repeated over a number of days. It was found that 

 reliable readings were obtained without waiting until some days after 

 drilling and in spite of nearby blasting. 



The conclusions drawn by the authors read as follows : ' Temperature 

 measurements in eight special drill holes in the Calumet and Hecla mines, 

 together with one in an old hole which has suffered no appreciable tempera- 

 ture change in ten years, all fall very nearly on a straight line. The 

 temperatures range from 74-75° F. at 3,562 ft. below the surface to 95-31° 

 at 5,679 ft. When taken in connection with Lane's value of 43° for the mean 

 surface temperature, these give an average temperature gradient of i° F. in 

 108-5 ft., or i° C. in 59-5 m., which is only about one-half of the Kelvin 

 average for the whole earth (1° in 27-76 m.). The gradient at an average 

 depth of 4,500 ft. is i° F. in 103 • 1 ft. 



' The data are not sufficient as yet to allow any positive conclusions as to 

 the time and extent of the glacial epochs, but point strongly to a value at 

 least as large as 30,000 years as the time which has elapsed since the last 

 epoch.' 



Mathematical Theory of Heat Flow in the Earth's Crust. 



By David Otto Ehrenburg. 



University of Colorado Bulletin, Boulder, vol. 32, no. 12, May 1932 ; The 

 University of Colorado Studies, vol. 19, no. 3, 1932, pp. 327-355. 



In the introduction to the mathematical discussion of the theory of heat 

 flow in the earth's crust given in this article, the author refers to Ingersoll 



