128 TRANSACTIONS OF THE [JAN. 22, 
by the first advance of the ice, and would, therefore, be included 
in the first or southern branch of the moraine. In other words, it 
should be looked for along the north shore only as far east as Port 
Jefferson, after which its occurrence would reasonably be ex- 
pected in the southern or Montauk Point branch. The Orient 
Point branch onght to consist, following the same course of 
reasoning, very largely of material left behind in the first re- 
treat of the ice, which would be pushed forward or transported 
by the second advance. That is, it ought to consist largely of 
previously eroded and transported material. As I have not 
traced the southern branch [ have had no opportunity to ex- 
amine the material composing it, but in regard to the northern 
branch the facts may be seen to be of considerable significance. 
It consists of water-worn and assorted quartzose and granitic 
sands and gravels, with but little till and few bowlders, and ap- 
parently not a trace of the characteristic ferruginous sandstones, 
shales and concretions derived from the material of the coastal 
plain, which are such prominent constituents of the moraine 
west of Port Jefferson. We have, in other words, just the con- 
ditions which would be inferred on the hypothesis of a second 
advance of the ice sheet. Further than this the rarity of 
bowlders and till might be expected from the probability that 
the trough eroded by the first advance of the ice had become 
filled with water and that in its second advance it would lose 
part of its load in passing over this body of water. A similar 
hypothesis, on a more extended scale, was advanced by Merrill* 
in order to account for the increasing rarity of bowlders and till 
throughout the entire morainal area east of Roslyn. This, how- 
ever, involves a discussion of the composition of the southern 
branch of the moraine, which is not included in this paper. 
We may next consider the facts in connection with the ‘ pre- 
glacial” or “ yellow gravel.” 
The principal difference of opinion between those who have 
studied this formation has arisen from the difficulty of deter- 
mining whence the material was derived which forms the gravel. 
Without entering into a discussion of the different views which 
have been advanced, it is sufficient to say that the general con- 
census of opinion at the present day is that we must look to 
eroded areas towards the northwest for the origin of this 
material. Should this hypothesis be correct, we ought to find 
the pebbles containing Silurian and Devonian fossils more 
abundant in the vicinity of areas of these rocks, in other words, 
in New Jersey, on Staten Island, and on the western end of 
* Mervill.—F. J. H. ‘‘On the Geology of Long Island.” Ann.N. Y. Acad. Sci, 
3: p. 359 (1885). 
