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On this continent one species, at least, had reached to the vicinity of its present habitat before the glaciation of the region.
Of this nature, among others, is a remarkable angular block of syenitic greenstone, 4 1/2 feet by 4 feet square, and 2 feet thick, which Mr. In Ireland we encounter the same difficulty as in Scotland in determining how much of the glaciation of the higher mountains should be referred to land glaciers, and how much to floating ice, during submergence.
Similar deposits prove glaciation in Norway succeeding the pre-Cambrian stage of elevation, and Cambrian glacial drift has recently been found in China. THE APPALACHIAN DEFORMATION. We have seen that during Paleozoic times a long, narrow trough of the sea lay off the western coast of the ancient land of Appalachia, where now are the Appalachian Mountains.
Over the lip of this cliff, and in the bed of the canyon above, and up the sides of the cliff-like walls, 1000 feet or more, the most perfect glaciation is found.
The reduction of the carbon-dioxide would be even more gradual. It is impossible to say how long it would take these processes to reach a very effective stage, but it is equally impossible to show that the interval between the upheaval and the glaciation is greater than the theory demands.
In Europe the Scandinavian plateau was the chief center of dispersion. At the time of greatest glaciation a continuous field of ice extended from the Ural Mountains to the Atlantic, where, off the coasts of Norway and the British Isles, it met the sea in an unbroken ice wall.
The backbone of our present system of determining the series of pre-historic epochs is the geological theory of an ice-age comprising a succession of periods of extreme glaciation punctuated by milder intervals.
Norway and Sweden appear to have passed through all the successive phases of glaciation which Greenland has experienced, and others which that country will one day undergo, if the climate which it formerly enjoyed should ever be restored to it.
The difference between the two parts of the State is not due to the underlying rock structure or to the rainfall except to a slight degree. Some of the difference is due to the fact that important cities such as Cleveland and Toledo lie on the fertile level strip of land along the lake shore, but this strip itself, as well as the lake, owes much of its character to glaciation.
Malldraeth Marsh is occupied by coal measures, and a small patch of the same formation appears near Tall-y-foel Ferry on the Menai Straits. A patch of granitic and felsitic rocks form Parys Mountain, where copper and iron ochre have been worked. There are abundant evidences of glaciation, and much boulder clay and drift sand covers the older rocks. Patches of blown sand occur on the S.W. coast.
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