THE HADLEY LAKE DRAINAGE. 585 



In the portion of the valley south of the entrance of the side valley 

 from the Leverett Lake this canyon is bordered by rou<^h ledg'es and till. 

 North of this the sands coming out of the side valley fill the main valley 

 from side to side with a great volume of coarse sands, cut only by the 

 northward prolongation of the canyon already noted. These sands pre- 

 serve for a long way a flat surface, but as they approach the north end of 

 the Mount Toby Valley the}' become gradually kettle-holed on a grand 

 scale, and as the valley widens the sands widen also and preserve their 

 height, 400 feet above sea, until they rest against the northernmost spur of 

 Mount Toby on the west and extend up along the mountain side on the 

 east, above the notch by which Locks Brook comes out of the mountains, 

 and a remnant still runs up into this notch. They end abruptly along a 

 broad curve (h^\ PI. XXXV, C), concave to northward, and sink down by 

 a slope as steep as sand will take to the level of the high terrace (336 feet 

 above tide) which formed the shore flats of the Montague Lake (see p. 615). 



It seems to me clear that the ice that filled the Montagiie basin pressed 

 into the north end of the Mount Toby Valley, compelling the waters of 

 Locks Brook (or Sawmill Brook) to find their way southwardly down this 

 valley and clogging the northern portion of the valley with lieavy sands; 

 and so far south as the kettle-holes extend, so far south the snout of the 

 ice was projected into the valley and heavily covered by the sands — the 

 kettle-holes being a measure of the portion which still remained unmelted 

 beneath the sands when the further recession of the ice allowed Locks 

 Brook to run directly westward into the Coiuiecticut, while the great con- 

 cave slope which bounds these sands (b", PI. XXXV, C) on the north marks 

 the shore line of the thicker ice, against which the sands were piled. 



The waters running southward through the canyon already described 

 cut a deep and narrow channel in the jointed qviartzite, where they seem 

 to have formed rapids, and at one place a distinct waterfall. They left no 

 deposits in this narrow part, but found it in flood time an insufficient outlet 

 and turned eastward through the side valley into the Leverett Lake, clog- 

 ging this with abundant sands. At the south end of this Mount Toby 

 canyon there remains on either side of its widened mouth a delta deposit 

 of rounded bowlders, 6 to 8 inches in size, from which all finer material is 

 removed, as a witness of the violence of the current, and farther south the 

 broad, level South Leverett plain (1 s h), west of Leverett railway station, 



