But it is now said that this implied magnitude of the glacial deposits on the lands skirting the New England coast is without foundation, since the larger bulk of these islands consists of upturned Cretaceous and Tertiary strata, which are only thinly covered with glacial débris, such as bowlders, gravel, clay, and sand, from the eroded shores of the mainland of New England. But it appears that the dislocated and folded cretaceous strata which underlie the glacial drift of Nantucket and Martha’s Vineyard were during an early period deposited on the bottom of a shallow sea, which then covered the Vineyard Sound, Buzzard’s Bay, and their surrounding lowlands. Thus the ice-sheets of the frigid age which moved over New England displaced the yielding stratified deposits of the shallow sea, and forced them southward in a disturbed condition to the position which they now occupy. Still, it is apparent that only a small portion of the glacial drift is found on these islands, which, according to appearances, must have been eroded and moved southward from the rocky lands of New England during the ice age; but there is sufficient to show that large quantities of such débris were carried over the islands into the Atlantic. And, judging from the eroded rocky New England lands, there must have been sufficient glacial drift moved over Nantucket and Martha’s Vineyard into the ocean beyond to far exceed in bulk the deranged Tertiary and Cretaceous deposits which now form so large a portion of the islands. For, when we look over lands bearing traces of the ice age, where the glaciers did not move their drift into the sea, so the terminal moraines of such glaciers can be better estimated, we can realize the great work that has been performed by the ice-sheet that overran New England during a frigid age. Professor James Geikie states, in his discussion on the glacial deposits of Northern Italy, that the deposits from Alpine glaciers of a frigid period “rise out of the plains of Piedmont as steep hills to a height of fifteen hundred feet, and in one place to nearly two thousand feet. Measured along its outer circumference, this great morainic mass is found to have a frontage of fifty miles, while the plain which it encloses extends some fifteen miles from Andrate southward.” And it is reported that there are found on the southern flank of the Jura numerous scattered bowlders, all of which have been carried from the Alps across the intervening plains, and left where they now rest. Many contain thousands of cubic feet, and not a few are quite as large as cottages.