Abstract
PROF. JOLY'S interesting discovery (NATURE, May 2, p. 8) that typical rocks in the Simplon Tunnel contain quantities of radium considerably in excess of the average of igneous rocks raises a question. From Mr. Strutt's investigations it appears that the average content of igneous rocks would be sufficient to account for the ordinary temperature gradient in the earth's crust were it due to radium. It seems, therefore, that, if the temperature was so caused, the gradient in the Simplon Tunnel ought to have been higher than the average, viz. 1° F. for between 50 feet and 60 feet. But, in fact, as beneath other mountains, it was considerably lower. In NATURE, October 27, 1904, it is stated that the temperature of the rocks in the advanced gallery was 108° F. where the cover was 7005 feet. This gives 1° F. for 92 feet. In the St. Gothard Tunnel it was 1° F. for 102 feet, and in the Mt. Cenis Tunnel 1° F. for 100 feet. That the gradient in the Simplon Tunnel, though low, was somewhat higher than in the other two was probably caused by the spring 23° hotter than the rock, which brought up heat from a lower level. I think I have shown in my “Physics of the Earth's Crust,” chapter xvi., that these low gradients-can but very slightly be attributed to the convexity of the surface.
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FISHER, O. Radium and Geology. Nature 76, 31 (1907). https://doi.org/10.1038/076031d0
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DOI: https://doi.org/10.1038/076031d0
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