E. Lewis— Water Cours 



tions they extend 

 wooded, rarely pre 



An inquiry is suggested, how and when were they formed ? 

 The surface waste of water from the present volume of rainfall 

 seems wholly inadequate to produce them. Much of this perco- 

 lates the soil after reaching the valleys, and in many instances 

 the bottom of the valleys, which is usually of travels and sand, 

 is covered deeply by an accumulation of sedimentary matter 

 because the flow of water through them has not been sufficient 

 to maintain them at their original dept.h. In the great water- 

 course which opens at Glen Cove there occurs, three miles south- 

 ward from its termination, a deposit of fine clay six feet or 

 more in thickness, and thirty feet below accumulated sediment 

 in the valley. The fact that such deposits occur in the old 

 water courses suggests, we think, feeble energy of erosion, and 

 points to a time when it was more active than now. 



The formation and maintenance of a vallev implies that the 

 material which filled it, or which might have" filled it, has been 

 removed by a stream of sufficient volume to accomplish the 

 work. A 'quantity of rainfall is conceivable which would 

 erode and deepen the valleys in question, and that such oc- 

 cured at a former period is quite possible, but we insist that 

 while some erosion must occur when water moves over the 

 surface of the ground, that the great development of these 

 valleys, espe i rce, and upon the highest grounds, 



is not explained by the «te The watershed of 



t i isi m ! u pun i ie ,,,'i - is narrow; frequently a few rods, or 



feet separates the so n >t i valley extending northward from 



one running southward. 



We are inclined to look to an agent other than rail 

 the development of the surface sculpture of Long Island. 

 Excepting its lower beds which may consist ot Tertiary or Cre- 

 taceous deposits, or of both, the island is a glacial moraine,— a 

 mass of debris both unmodified, and in every stage and form 

 of modification. The surface valleys were evidently water- 

 courses for - supplied by the ever wasting ice 



while it still lav upon the coast. From this cause a deep ero- 

 sion of the highest grounds was possible, and the general con- 

 tour erf the Si . The direction and course of all 

 « origin. So deeply 

 marked and well defined are they that little change n tfa r 

 general aspect seems to have taken place since the d 

 anee of the ice sheet from the coast. If from the surface valleys 

 we turn to the similar but vastly greater ones on the north side 

 of the island which now constitute the series of magnificent 

 harbors upon its coast, we find proof that they too had their 



