PLEISTOCENE GEOLOGY OF NASSAU CO. AND BOROUGH OF QUEENS 643 



halt is rather to be compared with those nearly stagnant ice fronts 

 which are marked over southeastern Massachusetts and in the Nar- 

 ragansett bay region by similar sand plains formed in the retreat 

 of the ice from the long maintained frontage on and against the 

 Cape Cod moraine, a stage everywhere on these islands marked by 

 well developed outwash plains. 



Glacial streams. The course of glacial streams escaping from 

 the ice front and extending over the frontal plain on tlie south side 

 of the island is plainly indicated by the creases extending from the 

 moraines near the head of the north shore harbors and from other 

 passes in the main moraine. The principal of these streams seem 

 to have followed tlie course of the harbors, if we may judge from' 

 the cross-section of the erosion channel or interruption of the 

 moraine where they crossed it. The most instructive of these chan- 

 nels across the moraine is at Koslyn ; there is another at Manhasset, 

 and still another less marked at the southern end of Greatneck bay. 



In each of these cases the larger valleys quite up to the pass 

 in the moraine appear to have been occupied by ice at the time 

 the ice sheet began to melt away. The thahveg north of the pass 

 or divide rises steeply, usually from the bay side, invariably much 

 steeper than the gradient of those valleys which, elsewhere on the 

 surface of the plains north of the moraine, have been interpreted as 

 older than the last ice advance. The pass in the moraine north of 

 Creed moor at the southern end of Little Xeck bay is about 150 feet 

 above sealevel ; that of Manhasset bay is about 170 feet. The Ros- 

 lyn channel is at about 130 feet. There is thus no accordance of 

 level in these outlets. 



Other passes across the main or inner moraine occur west of Ros- 

 lyn at about 230 feet, and east of Harbor hill at about 90 feet. 

 Southeast of Brook ville there is a pass at about 230 feet, and south 

 of East Norwich another at about 210 feet. All of these appear to 

 be more or less in line with certain valleys north of the moraine, 

 and all of them lead out south of the moraine into creases which 

 descend to the sea. 



The broad depression passing by Locust Grove toward East Nor- 

 wich is not wholly erosional in origin. Just north of the road at 

 Locust Grove the bottom descends into a large elliptic pit suggesting 



