Fj. Lewis — Water Courses on Long Island. 145 



proving the presence of the ocean over the region subsequent 

 to the deposit of the drift. The stratified beds occur at all 

 heights up to 260 feet aply a submergence of 



the coast to that extent. There still remained, however, many 

 elevations above the ocean (or if they were submerged their 

 contour was not altered), for they now show the same develop- 

 ment of old valleys as we have noticed on the north side of the 

 hills. This is important in explaining the newer valleys over 

 the stratified, and newer beds. We have traced several of these 

 to their source, and find that in each instance the new valley is 

 a continuation of an old one. These new valleys are called 

 locally "plain valleys," because they traverse the plains, and 

 there are thirty of them between East "New York and Riverhead, 

 a distance of fifty miles. 



It is easy to see why the new valleys are continuous with 

 those upon i ' i_l i _ in ! i 1 i i n upon the 



region would flow into the old valleys, giving direction to the 



which was probably the closing of the Glacial, or opening of 

 the Champlain period, would continually empty into the bay or 

 ocean near. As the coast arose from the water the shore line 

 receded, but the streams would still reach it, and slowly but 

 surely erode the plain valleys in question. It thus appears 

 that the water courses over the modi tied drift oft! pi is have 

 their origin in older valleys worn by glacial torrents in a pre- 

 ceding age. 



There is a source of valley erosion on both sides of Long 

 Island which has not yet been mentioned. It arises from springs 

 fed from rainfall, which break out and flow during the whole, 

 or part of the vear in some of the valleys. These springs are 

 from under-dramage. On the south side of the island they ap- 

 pear from one to three miles from the coast, forming streams of 

 great beauty and purity. It is from this source that the city of 

 Brooklyn is supplied with its wonderfully pure water. There 

 is reason to conclude that the springs broke out farther inland 

 at a former period. On the north side of the island springs 

 appear in some of the valleys trom which small streams flow a 

 part of the year. In both instances, however, we should not 

 expect the cropping out of springs, in valleys, until the valleys 

 were formed. It is because, in most in.-tanres. the valleys have 

 been cut down, to the level of saturation 



a »d if at anv period they cropped out farther inland in the 

 valleys, or upon a higher level, it was because the level of 

 saturation was higher than it now is. Anv subsequent lower- 

 ing of it has ari-'eii fro n dim lished supply of water, conse- 



In review the following conclusions seem to be sustained :— 



