JSL Lewis— Water -courses oj Southern Long Island. 215 



Art. XXV.— Certain features of the Valleys or Water-courses 

 of Southern Long Island; by Elias Lewis, Jr. 



That portion of Long Island which lies southward of its cen- 

 tral range of highlands, extending from near its western extrem- 

 ity to the Shinecock hills, is a plain, nearly level, traversed by 

 numerous shallow valleys or water-courses. There are about 

 thirty of these valleys, well defined, in a distance of fifty miles, 

 between East New York and Eiverhead, making one for a little 

 less than two miles. In the lower end of most of them are 

 flowing streams of singularly pure water, supplied bv under- 

 drainage of the region. The point where the springs break out 

 m the valleys represents the surface of saturation in the soil. 

 Above this point the valleys are dry excepting rarely when 

 streams occur from surface-drainage during freshets, or from 

 melting snow when the ground is frozen. 



Few of these valleys are more than twenty feet in depth; 

 their source is uniformly upon the high grounds, whence 

 they extend southward to the bay. In some cases they may be 

 traced nearly across the bay beneath its shallow waters to the 

 verge of the ocean, affording evidence of a recent subsidence 

 of the coast. A very marked peculiarity in their form is 

 the steepness or abruptness of the banks upon their westerly 

 sides, and the very gradual declivity of those upon their east- 

 erly sides. This feature is so obvious that it has long attracted 

 the attention of travelers, and of others acquainted with this 

 the island ; and we know of no exceptions to it which 

 cannot be explained by local conditions, such as may have 

 arisen from confluence of streams or similar causes. 



Another interesting feature of the valleys is their general di- 

 rection. With some local exceptions their general trend or direc- 

 tion is a little west of south, and observation of them through- 

 out their length renders it clear that this trend has arisen from 

 some general cause acting during their erosion. The westerly 

 or right banks have been eroded and worn away by the streams 

 which formed the valleys, and now that the streams have ceased 

 t0 m 1 i 0( ^ e tliem tae s teep banks remain. 



I he long declivities upon their easterly sides prove that the 

 axis of the stream was originally several rods, in some cases 

 trom an eighth to a fourth of a mile eastward of where the axis, 

 or deepest part of the valley now is. The phenomena we are 

 considering cannot be explained by any merely local cause 

 w 'th which we are acquainted. The valleys are of post-glacial 

 formation, and are in stratified gravels and sands distributed 

 °-Unng the Champlain subsidence, and were probably formed as 



