Wright.] 
138 
[January 19, 
boundary of this field crosses the state by a curve convex to the 
south from Perth Amboy to Belvidere on the Delaware River, 
about sixty miles above Trenton. As bearing in a general way 
upon the question in hand, we should mention the conclusions of 
Col. Charles Whittlesey in 1866, and of Prof. N. H. Winchell, T. 
C. Chamberlain, and R. D. Irving, a few years later, concerning 
the terminal moraine in Wisconsin and other western states. 
The investigations of Professor Hilgard touching the bluff depos- 
its in the lower Mississippi valley, and of Col. D. K. Warren upon 
those of the upper portion of this valley, are also of great signifi- 
cance in connection with this question. Nor should we fail to 
mention the extremely valuable papers of Professor J. D. Dana 
upon the condition of southern New England during the melting 
of the great glacier. (See Am. Journ. Science for 1875, Nos. 57, 
58, 59, and 60.) My own study of the kames and moraines of 
New England, the results of which are published in the Proceed- 
ings of this Society, and that of Mr. Warren Upham (see New 
Hampshire Geological Report, Yol. III.), and of Professor George 
H. Stone of Maine, serve to connect the operation of a wide- 
spread cause with the particular effects produced in the Delaware 
valley. It is also proper to repeat that the first announcement in 
1877 of the line of the terminal moraines across southern New 
England was made in a publication of this Society, in a commu- 
nication to the writer by Mr. Clarence King. (See Proceedings, 
Yol. XIX. pp. 50-63.) 
A second step in advance was made by the New Jersey geolo- 
gists (see Report for 1878, p. 22 ; Clay Report for 1878, p. 17) 
in recognizing a distinction between the implement-bearing grav- 
els of Trenton and the general deposit of yellow gravel which 
spreads over the southern part of the state. But the credit of 
accurately describing the peculiar character and limits of these 
Trenton gravels must be given to Professor H. C. Lewis, of Phil- 
adelphia. (See Proc. Min. and Geol. Section Acad. Nat. Sci., 
Phila., for Nov. 1878 and Nov. 1879.) 
A third step of great importance was also made by Professor 
Lewis in pointing out the relations of the Philadelphia brick clay 
to the other superficial formations of the Delaware valley. 
Having recently spent two weeks with Professor Lewis in going 
