COMSTOCK, Theodore Bryant, geologist, born in Cuyahoga Falls, Ohio, 27 July, 1849. He was graduated at the Pennsylvania state College in 1868, and at Cornell in 1870, where, in 1886, he received the degree of Ph.D. In 1870 he accompanied Hartt's expedition to Brazil as photographer and assistant geologist, and in 1873 was geologist to Capt. W. A. Jones's Wyoming expedition. He was director of the Kirtland summer school of natural history in Cleveland, Ohio, in 1875, and from that date till 1879 was professor of general and economic geology in Cornell. From 1879 till 1884 he was general manager of the Niagara consolidated mining company in Silverton, Col., for which he built and operated ore-sampling and concentrating works, after which he was elected to the chair of mining engineering and physics in Illinois University at Champaign. He has been prominent in the American association for the advancement of science, and in 1877 was chairman of the committee on Yellowstone park. In 1886 he was elected secretary of the section of geology and geography in this association. Dr. Comstock has made several important geological discoveries while on the various expeditions with which he has been connected, accounts of which have appeared in the "American Journal of Science," the "American Naturalist," the "Engineering and Mining Journal," and other journals to which he is a contributor. While in the west he edited the "San Juan Expositor" in Eureka, Col.. during 1879-'80, and was mining editor of the " Silverton Democrat " in 1882-'3. He has also published the geological portion of the "Report upon the Reconnoissance of Northwestern Wyoming, including the Yellowstone National Park" (Washington, 1875); "Outline of General Geology" (Ithaca,1878); "Classification of Rocks" (1877); "Notes en the Geology of San Juan Country" (1882); and"Geology and Vein-Structure of Southwestern Colorado" (1886), the two last from "Transactions of the American Institute of Mining Engineers."