210 T lie American Geologist. March, isaa 
CORRESPOIMDENCE. 
TuK Glactai. Gkology ok Martha's Vinkvakd Compakko \ViTit 
THAT OF Long Island. It is only recently that I had the j-leasureof read- 
iiiff jirofessor Shaler's report on the geology of Martlia's Vineyard, pub- 
lishedin theseventh annual report of the U.S. Geological Survey, and 
I was struck with the siniibirity between it and Long Island, including 
the plain country, as the professor calls it, south t)f the frontal 
moraine. In regard to the latter he is correct as to its origin, but at 
fault, 1 til ink, in the conjecture that the stratified deposits compos- 
ing it were laid down beneath the waters of the sea. I am aware 
that its counterpart, the south side of Long Island, has always been 
considered a dereliction from the ocean, but after years of careful 
study I have failed to discover anything marine in its composition. 
A few shells are said to have been found in digging wells, but a dili- 
gent search ft)r years on the part of the j)resent writer, has failed to 
reveal the slightest evidence of marine matter in these stratified de- 
posits. 1 presume it is the same with the plain country of [Martha's 
Vineyard, and I cannot conceive how streams laded with detritus 
could mingle with the waters of the ocean and maintain a separate 
existence. I'rofessor Shaler, however, thinks this is possible. He 
says: "At first sight, it may seem unlikely that the streams when 
poured into the sea. should be able to scour out channels for a mile 
or more beyond the ice front, but a similar work is performed where 
surface rivers enter the sea over the part of an extensive delta, 
though their currents were less rapid than those of sub-glacial 
streams urged as those streams were to their point of escape by the 
presence of ice as by the gravitative force given by their descent 
from the inland district." The professor is more competent to treat 
of this than the present writer; but I am very confident that future 
investigation will sliow that he is in error, at least, in regard to the 
presence of the ocean at the time when the plain country was being 
formed by snbglacial streams. Nor is there any evidence of oscilla- 
tion having taken place on these islands since the glacial age. I 
know it is dithcult to explain the different i)henomena on any other 
hypothesis, but some other explanation must be found. 
It is held, that Long Island existed as a littoral plain in preglacial 
times, and tliat tlie old shore line was some ninety miles south of the 
present ocean beacli, and that the land stood higher than now. 
flight it not have been //m// ///r ^^'u A r,7 //v(.s hurvr! The melting of 
the great continental ice-sheets must have had some effect on the 
ocean. The well at Woodhaven on the south side of Long Island 
reached the underlying rock at a depth of oOO feet below the present 
level of tiie sea. which is the depth oi the Hudson river gorge where 
it reaches the old shore line. Admitting that the Island had sunk 
this much in postglacial times, it is not likely that the subsidence 
