656 NEW YORK STATE MUSEUM 



makes it highly probable that for a time Hempstead harbor was 

 the site of a small glacial lake, at tii-st discharging at the 120 foot 

 level at lioslyii, and later by the SO foot channel into the Manhasset 

 water body. It now remains to determine whether the high level of 

 water in >ranhasset bay was then at sealevel or wht'ther it too was 

 held np by a glacial barrier. 



South of Manhasset is a col in the moraine, at an elevation of 

 alxint 175 feet, nuich higher than many cols separating the bay from 

 lower passes through the moraine in the country on the e^st of the 

 bay. It is evident that this col, which lies just east of Lake Sur- 

 prise, could not have been used as an outlet for the water confined 

 in Manhasset bay after the ice front had retired as far north as Port 

 Washington, for the water level had then fallen to 80 feet, as wit- 

 nessed bv the delta at that localitv. 



West of Manhasset bay, most of the region north of the moraine 

 fails to attain the 100 foot level. The moraine itself presents a con- 

 tinuous barrier rising above the 80 foot contour line at all points till 

 the vicinity of Maple Grove is reached. Between this locality and 

 Prospect park in Brooklyn, there are eight or nine low, troughlike 

 passes across the crest of the moraine, which might have served for 

 the overflow of water held in on the north between the moraine and 

 the retreating ice front as late as the Port Washington stage, while 

 the ice, on account of its greater activity near the axis of the Hud- 

 son lobe, maintained its position close to the moraine in the vicinity 

 of Brooklyn, at least depassing the 80 foot contour line on the back 

 of the moraine so as effectually to prevent discharge by a lower 

 level into New York bay north of the Narrows. 



These troughs across the moraine are singularly uniform in level. 

 In all those enumerated their bottoms lie according to the govern- 

 ment survey between the 100 foot and the 80 foot contour lines. 

 Some of them are clearly inosculating kettle-holes, marking the site 

 of melting masses of the ice. From some of them, drainage creases 

 can l>e traced out over the frontal plain. They are best developed 

 in line with the bays and depressions on the north side of the 

 moraine, and hence were probably the paths of subglacial streams, 

 as in the case of the passes on the Oyster Bay rpiadrangle. They 

 are however not unicpie in this portion of the moraine. There are 



