730 



SCIENCE. 



[X. S. Vol. XVIII. Xo. 4GG. 



number of new facts, some of them of quite 

 far-reaching importance, were established by 

 the resurvey of the island by the Division of 

 Hydrology,* United States Geological Survey 

 during the past summer. The more important 

 results are included in the following su mm ary : 



1. Long Island, instead of consisting almost 

 entirely of glacial deposits, as was once 

 thought, is now known to possess throughout 

 a large portion of its extent a core of older 

 Cretaceous beds, rising in places to nearly 300 

 feet above sea level. 



2. These Cretaceous beds are not lim.ited to 

 the north shore, as has frequently been sup- 

 posed, but rise nearly to the tops of the highest 

 hills and estend far to the south, either at the 

 surface, as in the West Hills, or at slight 

 depths beneath the gravel plain on the south 

 side of the island. 



3. This Cretaceous nucleus has been found 

 to have been deeply eroded before the deposi- 

 tion of the earliest glacial deposits. 



4. The present field work has led to the dis- 

 covery of greensand in the West Hills, thereby 

 suggesting if not establishing the Upper Cre- 

 taceous age of the deposits in question. A 

 considerable thickness of the underlying black 

 and chocolate clays may also be of the same 

 age. 



5. The dip of the ' Cretaceous of the north 

 shore has been determined for the first time, 

 well records showing it to be, in the Oyster 

 Bay region, south 23° east and about 65 feet 

 per mile. 



6. The absence of the great masses of Ter- 

 tiary clays and gravels, assumed to be pres- 

 ent by earlier workers, was established be- 

 yond question. 



7. The yellow gravels formerly assigned to 

 the Tertiary, and considered as constituting 

 a considerable mass overlying the supposed 

 Chesapeake (Tertiary) clays, have been shown 

 to constitute the first of the glacial series 

 (probably Pre-Kansan) of the Quaternary, 

 and normally to underlie the clays instead 

 of overlying them. The gravels were greatly 



* Executive and areal work was in charge of 

 M. L. Fuller, and the underground geology and 

 water problems were in charge of A. C. Veatch. 



eroded before the deposition of the clays, 

 the deep valley reaching 280 feet below the 

 present sea level which underlies Jamaica, 

 and Jamaica Bay, and which seems to be the 

 logical continuation of the submerged valley 

 shown by the soundings of the Coast and Geo- 

 detic Survey off New York harbor, probably 

 being completed if not largely formed at this 

 time.. 



8. The supposed Chesapeake clays have been 

 differentiated into three distinct formations: 

 the first including the clays near Bethpage 

 and Wyandance being referred to the Creta- 

 ceous; the second comprising the buried clays 

 beneath Jamaica and Jamaica Bay belonging 

 to an early interglacial (probably Yarmouth), 

 and the third including East Williston and 

 similar clays to the late glacial (Wisconsin) 

 stage. 



9. The portion of the supposed Chesapeake 

 clays beneath Jamaica, Jamaica Bay, etc., 

 were shown to be underlain by glacial gravels 

 of the second ice invasion (probably Kansan), 

 while the clays themselves were proved to 

 have been deposited in the interglacial period 

 (Yarmouth) between the second and third 

 invasions. The area of the clays has been 

 traced out by borings, and the clays themselves 

 shown to represent salt marsh, or submarine 

 deposits formed around the Cretaceous core 

 when the land stood fifty feet higher than at 

 present. 



10. The Icnown areas of the Manhasset 

 gravels have been greatly extended to the 

 south and east, having been recognized at 

 Eockaway Eidge, Barnums Island, Bethpage, 

 Half Hollow Hills and eastward beneath Shel- 

 ter Island, and on the south fiuke nearly to 

 Montauk. Its age is probably lowan. 



11. The Manhasset gravels have been proved 

 normally to underlie the moraines instead of 

 resting against them as has sometimes been 

 urged. Actual sections showing the relations 

 were found. 



12. Very little of the total height of the 

 ridges is generally due to the morainal de- 

 posits themselves, the moraines either resting 

 upon or constituting a coating over the older 

 Manhasset, Pensauken or Cretaceous beds 

 constituting the main mass of the elevations. 



