Such blocks are found on the Jura, at a height of no less than two thousand feet above the Lake of Neuchâtel. The Jura Mountains being formed of limestone, it is easy to distinguish the débris deposited by Alpine glaciers; and, from what I can learn of extensive glacial work, it appears that intervening plains, lakes, and sounds are so often found separating the source of ancient glaciers from their deposits that their existence becomes almost necessary to represent the general outlines of disturbance performed during an ice period. In consideration of such facts and the foregoing statements of reliable observers, I am prompted to offer my views on glacial work performed on a portion of the Pacific shores of North America, which seems to me to be much more extensive than hitherto supposed. Professor Whitney describes the coast mountains of California as being made up of great disturbances, which have been brought about within geologically recent times; and this statement I found to be so obvious in my travels over that region that it appears to me that the coast ranges originated in a different manner from the older Sierras. The western sides of the latter mountains everywhere show the great eroding power of ancient glaciers; and, when I considered their favorable position for the accumulation of snow during a glacial period, I was led to seek for the glacial deposits adequate to represent the great gathering of ice which an age of frigid temperature would produce. But it seemed to me that such deposits could not be found in the foot-hills of the Sierras, which contain the moraine of inferior ice-sheets that terminated at the base of the mountains. Under these conditions I came to the conclusion that during the earlier ice period the immense glaciers which must have formed on the western slopes of the Sierra range moved their gigantic accumulation of débris so far seaward as to form the range of hills now existing next the coast line, and perhaps the islands abreast the Santa Barbara coast, the Contra Costa, or eastern range, being formed during a subsequent ice period, in the same manner as the hills next the coast line.