144 R Lewis— Water Courses on Long Island. 



origin in glacial times. These harbors are eight in number, and 

 although in glacial drift are as truly fiords as those along the 

 rocky coast of Greenland. They extend into the island from 

 three to six miles, they are from half a mile to a mile and a 

 half broad and are in the deeper portions from ten to twenty- 

 five feet deep. They were probably deeper when free from 

 sediment. In a few instances v ts are strong 



the water is from thirty to fifty feet deep. The land on either 

 side of the fiords is from a few feet to as much as 200 feet 

 above tide, and the valleys continue long distances inland 

 beyond where the tides reach. Many lateral valleys open into 

 these, evidently cut by glacial streams. It is extremely prob- 

 able that these great fiords were, at an early stage of the 

 formation of the island, water-courses opening to the ocean, and 

 were maintained as such until filled by accumulating drift. 

 This may have occurred while tbe ice sheet still lay over the 

 region, and the streams were under or sub-glacial ones. When 

 however the valleys were finally filled with drift at their ter- 

 minus the waters were arrested, and thenceforth discharged 

 eastward and westward through, what is now, Long Island 

 Sound. 



There is no evidence that the fiord valleys have changed in 

 their general contour since the glaciers disappeared. The facts 

 undoubtedly imply that the coast stood at a greater elevation 

 than now, for tbe glacial-fed streams must have swept the fiord 

 valleys to their bottom. But Prof. Dana has shown long since 

 that the Glacial period was probably one of elevation of North- 

 ern lands. 



There is reason for tbe conclusion, however, that some deep- 

 ening of the principal surface valleys has taken place subse- 

 quently to the disappearance of the ice, which may be attributed 

 to streams. There occurs in many instances fragmental depos- 

 its of sand and gravel along their banks, ten to twenty or 

 more feet above the bottom, which seem to be remains of flood 

 plains, and indicate erosion to that extent If this be correct, a 

 more abundant rainfall at a former period is suggested, and it 

 e occurred while the ice still lav upon New England. 

 Chilled by its presence the vapor-laden air from tbe ocean 

 might have dropped its moisture in more abundant rain or snow 

 upon the coast, and local accumulation of snow upon the hills 

 ' t iiiuv have aided in swelling the eroding streams. 



The water-courses which open southward from the central hills 

 of the island extend over a nearly uniform plain; they are of 

 moderate depth, rarely greater than twenty feet, have few tribu- 

 taries, and are quite din -t and < <mtin ions fi >sn the hills to the 

 bay. They are over a formation geologicall v different from that 

 on the north side of the hills, it be ■ -I and sand, 



