EXPERIMENTS IN THE FIELD: GEORGE BECKER, CARL BARUS AND GEOLOGICAL EXPERIMENTATION AT THE COMSTOCK LODE

Between 1865 and 1877, three different distinguished mining experts studied the prolific silver mines of the Comstock Lode on three separate occasions. Despite this attention, in 1880 Clarence King, first director of the United States Geological Survey and one of those experts, tasked geologist George Becker with performing a definitive study of the Comstock as one of the bureau's first monographs. King instructed Becker to investigate several specific geophysical problems concerning the ore deposits, including the controversial proposition that the extraordinary heat at depth in the mines was due to the exothermic decomposition of feldspathic rocks to kaolin, and whether the lode had detectable electrical activity. Becker hired physicist Carl Barus to lead both research projects. Through a series of delicate experiments measuring heats of decomposition, Barus found that the temperatures at depth could not be explained by kaolinization, supporting Becker's larger geological claim for local volcanic action as the source. Barus also determined that the electrical activity of ore bodies though faint was detectable and could potentially be used as a means of mapping and prospecting. This incorporation of physical analysis into geological reasoning proved a powerful tool for Survey geologists as they looked to establish an authoritative voice in the field of mining geology with its abundance of private, well-paid experts. The story of the experiments also illustrates the physical and epistemological difficulties of doing experimental work in the field and how the Survey's mining geological work guided the growth of experimental analysis in American geology.