THE AMERICAN MIDLAND NATURALIST. 



sand and the evidence is that it originally was a natural 

 prairie in the midst of a generally wooded region. The 

 south plain is somewhat more extensive than the north plain, 



(which is between the two moraines), and ranges in width 

 from less than a mile to more than 10 miles. A large tract 

 of the surface of the south plain in the vicinity of Mineola, 

 Hempstead and Camp Mills has always been open prairie, 

 but elsewhere both the north and south plains were once 

 covered with scrub oaks, scattered pines and underbrush 

 and the terms "brushy plain" and "pine plain" which were 

 in early days used to distinguish parts of them from the 

 Hempstead plains, are still widely applicable. In North 

 Hempstead the south plain stands 120 ft. above sea level, 

 but north of Hicksville it rises to 200 ft. It is not much cut 

 by sharp ravines or valleys, but is traversed from north to 

 south by a series of channels 10-20 ft. deep, in the bottom 

 of which springs issue and feed small streams that flow 

 through the southern third of the plain, finally discharging 

 into the marsh bordered channels at the south shore. Harper 



('12, '18) has made a valuable study of the vegetation of 

 this natural prairie, relating it to the geological conditions 

 indicated. The prairie is within 5 miles of Cold Spring 

 Harbor. Hicks (1892) first comprehensively listed the 

 plants from this region. 



The valleys of Long Island are generally free from- con- 

 spicuous branching as would be expected if produced by the 

 ordinary process of stream erosion. On the borders of each 

 main valley are many smaller later valleys sloping toward 

 the harbors, and more or less filled with late drift. Some 

 of the original valleys of Long Island are buried, and were 

 formed by glacial waters as well as by existing streams. The 

 valleys in the Manhasset formation (Pleistocene) are every- 

 where conspicuous, having been cut from an elevation of 

 200 ft. Most have become modified from the action of the 

 ice or the deposition of glacial debris. In many the modifi- 

 cations are confined to the deposition of a superficial mantle 

 of drift. There may be low morainal accumulations on the 

 valley sides such as that at Cold Spring Harbor. The 

 slope of the bottoms of the valleys is usually gentle, 10-15 

 feet per mile, and they flatten in the lower mile or two per- 



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