4 The American Geologist January. 1897 
plains, the meadows and sands of Manhattan ishxnd, and the 
marine deposits along lake Cham])lain and Hudson river. 
Thirdly, came the sabject of the Drift — erratics, hardpan, 
lists of striai, both for New l'"ork and other states. The de- 
scription of the distribution of boulders and till over Long- 
island is very full and complete, and was used by the writer 
in the preparation of a paper presented to the Lyceum of 
Natural History in New York and the Long Island Historical 
Society in 1868, entitled " The Geological History of Long 
Island.'' The facts of Mather's report were employed to il- 
lustrate the theory that the backbone of Long island consti- 
tuted a part of the terminal moraine of the ice-sheet. Mr. 
Mather, however, followed his cnntemporaries in supposing 
that the dispersion of the boulders and the striation of the 
ledges resulted from floating ice in a time of general submer- 
gence. His objection to Agassiz's glacial theory was the com- 
mon one of his day — that the flat lands of the middle western 
states did not olfer a sufficient slope to produce motion in the 
ice-sheet. Owing to his connection with survej^sin other states 
he says his conclusions were based upon what he had seen in 
over one hundred thousand miles of travel. 
The study of the formations of Long Island enabled 
Mather to recognize botli the Tertiary and the Cretaceous, 
though he used a local name for the group. The outcrops of 
the Trias were rather limited, but he correlated the sand- 
stones with those of the Connecticut valley, and he suspected 
that the associated trap rocks might have been ejected in the 
Cretaceous. For the proper explanation of the distribution 
of the Trias in the Connecticut and Newark areas, with op- 
posite dips, Mather first states and rejects the fluviatile h}'- 
pothesis of H. D. Rogers and then proposes a new theory 
based upon the courses of the equatorial or gulf stream and 
of the returning polar current. The first stream being direct- 
ed through the Connecticut valley v/ould naturally deposit 
sediment upon an easterly slope, and the returning polar cur- 
rent having a westerly tendency would drop its burdens upon 
the Palisade side of the Hudson. 
No part of this report has attracted more attention than 
his conclusions respecting the rocks east of the Hudson river. 
His colleague, Emmons, as is well known, had proposed an 
