In 1866 Professor J. D. Whitney discovered the famous 'Calaveras' skull at a depth of about a hundred and thirty feet in a bed of auriferous gravel on the western slope of the Sierra Nevada, California. The skull rested on a bed of lava, and was covered by several layers of lava and volcanic deposit. Many other remains were found in similar geological positions, and this was thought to prove that the Calaveras skull was not an isolated instance of the presence of man in America in Tertiary times. The skull resembles the Eskimo type, and chemical analysis discovered the presence of organic matter. These circumstances led to the conclusion that the great age claimed by Whitney for the relic was by no means proved, and this view was strengthened by the knowledge that displacements of the deposits in which it had been discovered had frequently been caused by volcanic agency.
More recent finds have been summarized by an eminent authority connected with the United States Bureau of Ethnology as follows: "In a post-Glacial terrace on the south shore of Lake Ontario the remains of a hearth were discovered at a depth of twenty-two feet by Mr. Tomlinson in digging a well, apparently indicating early aboriginal occupancy of the St. Lawrence basin. From the Glacial or immediately post-Glacial deposits of Ohio a number of articles of human workmanship have been reported: a grooved axe from a well twenty-two feet beneath the surface, near New London; a chipped object of waster type at Newcomerstown, at a depth of sixteen feet in Glacial gravel; chipped stones in gravels, one at Madisonville at a depth of eight feet, and another at Loveland at a depth of thirty feet. At Little Falls, Minn., flood-plain, deposits of sand and gravel are found to contain many artificial objects of quartz. This flood-plain is believed by some to have been finally abandoned by the Mississippi well back toward the close of the Glacial period in the valley, but that these finds warrant definite conclusions as to time is seriously questioned by Chamberlain. In a Missouri river-beach near Lansing, Kansas, portions of a human skeleton were recently found at a depth of twenty feet, but geologists are not agreed as to the age of the formation. At Clayton, Mo., in a deposit believed to belong to the loess, at a depth of fourteen feet, a well-finished grooved axe was found. In the Basin Range region, between the Rocky Mountains and the sierras, two discoveries that seem to bear on the antiquity of human occupancy have been reported: in a silt deposit in Walker River Valley, Nevada, believed to be { 10} of Glacial age, an obsidian implement was obtained at a depth of twenty-five feet; at Nampa, Idaho, a clay image is reported to have been brought up by a sand-pump from a depth of three hundred and twenty feet in alternating beds of clay and quicksand underlying a lava flow of late Tertiary or early Glacial age. Questions are raised by a number of geologists respecting the value of these finds."