CHAPTER V. ANCIENT GLACIERS IN THE WESTERN HEMISPHERE. New England. IN North America all the indubitable signs of glacial action are found over the entire area of New England, the southern coast being bordered by a double line of terminal moraines. The outermost of these appears in Nantucket, Martha's Vineyard, No Man's Land, Block Island, and through the entire length of Long Island-from Montauk Point, through the centre of the island, to Brooklyn, N. Y., and thence across Staten Island to Perth Amboy in New Jersey. The interior line is nearly parallel with the outer, and, beginning at the east end of Cape Cod, runs in a westerly direction to Falmouth, and thence southwesterly through Wood's Holl, and the Elizabeth Islands -these being, indeed, but the unsubmerged portions of the moraine. On the mainland this interior line reappears near Point Judith, on the south shore of Rhode Island, and, running slightly south of west, serves to give character to the scenery at Watch Hill, and thence crops out in the Sound as Fisher and Plum Islands, and farther west forms the northern shore of Long Island to Port Jefferson. In these accumulations bordering the southern shore of New England, the characteristic marks of glacial action can readily be detected even by the casual observer, and prolonged examination will amply confirm the first impression. The material of which they are composed is, for the most part, foreign to the localities, and can be traced to outcrops of rock at the north. The boulders scattered over the surface of Long Island, for example, consist largely of granite, gneiss, hornblende, mica slate, and red sandstone, which are easily recognised as fragments from well-known quarries in Connecticut, Rhode Island, and Massachusetts; yet they have been transported bodily across Long Island Sound, and deposited in a heterogeneous mass through the entire length of the island. Not only do they lie upon the surface, but, in digging into the lines of hills which constitute the backbone of Long Island, these transported boulders are found often to make up a large part of the accumulation. Almost any of the railroad excavations in the city of Brooklyn present an interesting object-lesson respecting the composition of a terminal moraine. All these things are true also of the lines of moraine farther east, as just described. Professor Shaler has traced to its source a belt of boulders occurring extensively over southern Rhode Island, and found that they have spread out pretty evenly over a triangular area to the southward, in accordance with the natural course to be pursued by an ice-movement. Nearly all of Plymouth County, in southeastern Massachusetts, is composed of foreign material, much of which can be traced to the hills and mountains to the north. Even Plymouth Rock is a boulder from the direction of Boston, and the "rock-bound" shores upon which the Pilgrims are poetically conceived to have landed are known, in scientific prose, as piles of glacial rubbish dumped into the edge of the sea by the great continental ice-sheet. The whole area of southeastern Massachusetts is dotted with conical knolls of sand, gravel, and boulders, separated by circular masses of peat or ponds of water, whose origin and arrangement can be accounted for only by the peculiar agency of a decaying ice-front. Indeed, this whole line of moraines, from the end of Cape Cod to Brooklyn, N. Y., consists of a reticulated network of ridges and knolls, so deposited by the ice as to form innumerable kettle-holes which are filled with water where other conditions are favourable. Those which are dry are so because of their elevation above the general level, and of the looseness of the surrounding soil; while many have been filled with a growth of peat, so that their original character as lakelets is disguised. As already described, these depressions, so characteristic of the glaciated region, are, in the majority of cases, supposed to have originated by the deposition of a great quantity of earthy material around and upon the masses. of ice belonging to the receding front of the glacier, so that, when at length the ice melted away, a permanent depression in the soil was left, without any outlet. To some extent, however, the kettle-holes may have been formed by the irregular deposition of streams of water whose courses have crossed each other, or where eddies of considerable force have been produced in any way. The ordinary formation of kettle-holes can be observed in progress on the foot of almost any glacier, or, indeed, on a small scale, during the melting away of almost any winter's snow. Where, from any cause, a stratum of dirt has accumulated upon a mass of compact snow or ice, it will be found to settle down in an irregular manner; furrows will be formed in various directions by currents of water, so that the melting will proceed irregularly, and produce upon a miniature scale exactly what I have seen on a large scale over whole square miles of the decaying foot of the great Muir Glacier in Alaska. The effects of similar causes and conditions we can see on a most enormous scale in the ten thousand lakes and ponds and peat-bogs of the whole glaciated area both in North America and in Europe. In addition to these two lines of evidence of glacial action in New England, we should mention also the in |