at an elevation of 4,660 feet on the base of the Rocky Mountains. The boulder clay, when thick, can be seen to be rudely stratified, and at one place includes beds of laminated clay with compressed peat, similar to the forest beds described by Worthen and Andrews in Illinois, and the so-called interglacial beds described by Hinde on Lake Ontario. The leaf beds on the Ottawa river, and the drift trunks found in the boulder clay of Manitoba, belong to the same category, and indicate in the midst of the Glacial period many forest oases far to the north, having a temperate rather than an arctic flora. In the valleys of the Rocky Mountains opening on these plains there are evidences of large local glaciers now extinct, and similar evidences exist on the Laurentian highlands on the east. A recent paper of Dr. G. M. Dawson on the Palæography of the Rocky Mountains illustrates in a most convincing manner the changes which have occurred in the Cordillera of North America, and the differential elevation and depression which have affected its climate in the later geological periods.[169] [169] _Transactions Royal Society of Canada_, 1890. Perhaps the most remarkable feature of the western drift region is that immense series of ridges of drift piled against an escarpment of Laramie and Cretaceous rocks, at an elevation of about 2,500 feet, and known as the "Missouri Coteau." It is in some places 30 miles broad and 180 feet in height above the plain at its foot, and extends north and south for a great distance: being, in fact, the northern extension of those great ridges of drift which have been traced south of the great lakes, and through Pennsylvania and New Jersey, and which figure on the geological maps as the edge of the continental glacier--an explanation obviously inapplicable in those western regions where they attain their greatest development. It is plain that in the north it marks the western limit of the deep-water of a glacial sea, which at some periods extended much farther west, perhaps with a greater proportionate depression in going westward, and on which heavy ice from the Laurentian districts on the east was wafted south-westward by the arctic currents, while lighter ice from the Rocky Mountains was being borne eastward from these mountains by the prevailing westerly winds. We thus have in the west, on a very wide scale, the same phenomena of varying submergence, cold currents, great ice floes and local glaciers producing icebergs, to which I have attributed the boulder clay and upper boulder drift of eastern Canada. In short, we arrive at the conclusion that there never has been a continental glacier, properly so called, but that in the extreme Glacial period there have been great centres of snow and glacial action, in the Cordillera of the west, in the Laurentian plateau of the north, and in the northern Appalachians, and the Adirondacks, while the lower lands have been either submerged,