Wave-like hills of sand cap the embankments in several localities north of Hatfield and North Hadley. Some, perched on the terrace edge, were partly cut away when the river was establishing the limits of its floodplain. Wherever the pine trees are cut down, or the grass plowed under, the sand within these hills begins to drift. They look and act like those hills of the desert, the sand dunes, and they record the drift of wind-whipped sand across a naked land, before the river had established a floodplain within its present confines. _The Landscape Changes_ Fine sand, silt, or clay is found beneath the windblown sand wherever the river banks undercut the dunes. The clays are especially widespread, for each of the numerous local brickyards has its clay pit, and there are many more clay banks which have no brickyard. The clays are rhythmically banded. One band, composed of very fine material which settles from suspension only after weeks of absolute quiet, retains moisture tenaciously; adjacent bands dry more rapidly, are somewhat sandy, and settle from suspension in less than a week. A large body of quiet water in which so much fine clay could settle must have occupied the valley before the river was there, and the only type of water body which could have provided the proper environment is a fresh-water lake, free from agitation during the long winter months when its surface was frozen over. These thin clay bands are deposits of a winter season, when streams are low and their load light. Then, even the finest particles can settle, during the many weeks of quiet water, as a paper-thin layer upon the lake bottom. The coarser sandy layer just above the finest clay records the spring break-up, the melting of the ice, and resuscitated streams flowing from the hills with a vigor that can be acquired only when the melt-water from the winter snow combines with the normal run-off. The sand which these freshets bring to the lake diminishes as the spring floods subside, and the sediment becomes progressively finer until next spring comes around. Pl. 2. _Features of the landscape which originated during comparatively recent time._ [Illustration: a. _Air view of the ox-bow lake between Northampton and Mt. Tom._] [Illustration: b. _Roches moutonnées of the Pelham Hills seen from Hadley._] [Illustration: Fig. 3. _Block diagram showing the main features of central Massachusetts at the present time._] [Illustration: Fig. 4. _Block diagram showing the main features of central Massachusetts during the recession of the Ice Sheet._]