332 The American Geologist. May, 1891 
enty years. Borings made for salt water were annoyed by the outflow 
of gas and oil at a depth of about 200 feet, but these substances have 
never been brought into economic notice. The report gives also the 
results of an examination into the soils, both chemical and mechanical. 
CORRESPONDENCE. 
Excursion Across Long Island. Having spent a vacation of four 
weeks last summer at Eastport, L. I., N. Y., near the centre of the 
island, an opportunity was afforded of renewing my study of the drift 
phenomena on that wonderful little isle by the gate of the sea. During 
my stay, at Eastport I made an excursion across the island to Wading 
River. A walk of about three miles brought me to the so-called "Back- 
bone " supposed to mark the terminal front of part of the great continen- 
tal ice-sheet, or Laurentide glacier. The boulders begin to be quite 
plentiful and the glacial till is easily recognized. 
After leaving Manor however, the boulders begin to disappear and 
few are seen in crossing the Riverhead valley — an old subglacial river 
channel — until Wading River is reached and where the northern series 
of hills rise along the sound. Here again the erratics are met with in 
abundance and are much larger than those seen along the line of the 
terminal moraine at Manor. I had been inclined to believe that geolo- 
gists were in error in supposing that these two moraines represented 
two separate Glacial epochs, as I never could see any evidence of more 
than one, but this trip across the island tended to shake my faith in the 
one glacial movement, for if one ice-sheet covered the whole island at 
the same time, how is it that no boulders are found in the intervening 
valley ? 
At first I was sorely puzzled. Another problem presented itself. I 
saw that the boulders at Wading River far exceeded in size any we had 
noticed along the southern ridge and it occurred to me that this was 
proof of two distinct ice-sheets, for one glacier would not be likely to 
drop all of the large erratics on the north side of the island. 
A subsequent visit to Rock hill, however, cleared away some of those 
doubts, for there on the very summit of the southern ridge, or back- 
bone as it is called, was an immense boulder similar to those at Wad- 
ing River. The natives have been quarrying from it for the past hun- 
dred years cr so, and yet this erratic from which the hill derives its 
name, is more than fifty feet in circumference and about twenty feet 
in night for it stands up among the pines like a huge monument, or 
obelisk, in the desert. It is very impressive. It looks as if it might 
have been dropped by floating ice. but it would be strange if floating ice 
would drop its burden directly on the summit of the terminal moraine ; 
besides this huge erratie'lies directly in the path of the glacier on its 
" march to the sea." It is a coarse gneissic granite and must have been 
torn from the same parent rock as those of the same kind seen at Wad- 
ing River. 
