"The deposits are so indurated as to serve for building-stone. They have been upturned in many places by the uplifting of mountains. Elsewhere they have been divided by faults, and the fragments, dissevered from their continuation in the valley, have been carried high up on the mountain-flanks, where erosion has carved them in typical mountain forms.... The date of the Bonneville flood is the geologic yesterday, and, calling it yesterday, we may without exaggeration refer the Pliocene of Utah to the last decade; the Eocene of the Colorado basin to the last century, and relegate the laying of the Potsdam sandstone to prehistoric times."[EJ] [Footnote EJ: Second Annual Report of the United States Geological Survey, p. 188.] Mr. Russell adds to this class of evidence that of the small extent to which the glacial striæ have been effaced since the withdrawal of the ice from the borders of these old lakes: "The smooth surfaces are still scored with fine, hair-like lines, and the eye fails to detect more than a trace of disintegration that has taken place since the surfaces received their polish and striation.... It seems reasonable to conclude that in a severe climate like that of the high Sierra it" (the polish) "could not remain unimpaired for more than a few centuries at the most."[EK] [Footnote EK: See also Mr. Upham in American Journal of Science, vol. xli, pp. 41, 51.] Europe does not seem to furnish so favourable opportunities as America for estimating the date of the Glacial period; still it is not altogether wanting in data bearing upon the subject. Some of the caves in which palæolithic implements were found associated with the bones of extinct animals in southern England contain floors of stalagmite which have been thought by some to furnish a measure of the time separating the deposits underneath from those above. This is specially true in the case of Kent's Cavern, near Torquay, which contains two floors of stalagmite, the upper one almost continuous and varying in thickness from sixteen inches to five feet, the lower one being in places twelve feet thick, underneath which human implements were found.