216 The American Geologist. October, i892 
evittil)ly si;pply an aliundtint (juantity of ferruginous material to 
the deposits at its Ijase. 
The interpretation given to these extra-morainic deposits must 
of necessity have its bearing upon the question as to the exist- 
ence of an earlier ice-sheet which once covered the state of New 
Jersey as far south as Trenton and the line of the yellow gravels. 
So far as the deposits which we have discussed can be referred to 
the later ice-sheet, or to water transportation or to any other sim- 
pler and sufficient causes so far, of course, they must fail to give 
support to the theor}' of an earlier ice-sheet. 
While not wishing to enter fully at the present time upon a 
discussion of the existence of such an ice- sheet in the past, I 
will, in closing, mention two points, which while negative, would 
still seem to have something more than a negative bearing against 
such a supposition. 
The first is, that no such ice-sheet has done duty in depositing 
northern material over the large Triassic area of Hunterdon county. 
Not a northern pebble could I find upon the high plateau west of 
Flemington, in the region about Cherryville, Quakertown, Croton 
and Little York, where the elevation is from 500 to 650 feet. Nor 
are there any on the low ground at Flemington and southward and 
eastward, where the elevation is from 125 to 250 feet. At hundreds 
of places the entire thickness of the soil is exposed down to the 
rock in place, and the complete identity of the soil with the un- 
derl3'ing rock, without any foreign admixture, is perfectly clear. 
Finally there may be added one critical test, of the same sort, 
to which this supposed ice-sheet has failed to respond. It has 
failed to disturl) the fragments of trap rock that lie upon the sum- 
mit of Sourland mountain, where they have l)een exposed to the 
Aveather presumably since the close of the Jurassic age. Sour- 
land mountain is a low swell, reaching an altitude of aliout 500 
feet and extending from Neshanic, southwestwardly to the Dela- 
ware river at Lambertville. The center line is trap while this is 
flanked on both sides by indurated Triassic shales. 1 have crossed 
this mountain at three difl'erent places, at Buttonwood Corners, at 
a point two miles west of Rocktown and at Lambertville, and at 
no point do these dial)ase bowlders appear to have been carried 
over upon the borders of the Triassic, by any force whatever, not 
even by gravit}'. It is difficult to see how an ice-sheet could 
have passed over without transporting some of these fragments. 
