6 
Frank Carney 
it has a thickness of thirty feet, the greatest thickness it is known i 
to possess. Its stones, so far as they are of decomposable rock, 
are decayed. From it most of the calcareous matter has been 
leached. ‘‘The constitution of the drift is, in a general way, 
comparable to that of the younger drift. It contains materials ! 
of all grades, from huge bowlders to fine clay.’’ “Limestone is | 
rarely present. When the drift occurs in quantity, glaciated stones 
are by no means rare. ‘‘ It generally lacks all indication of struc- ; 
ture, though foliation is to be seen in someof the deeper exposures.” || 
“In its constitution, and in the relations of its constituents, the j 
drift corresponds with till.”^'^ i| 
It should be noted, however, that Salisbury does not find the || 
extramorainic drift in New Jersey uniform in the stage of weather- [l 
ing attained for this reason he suggests that, while most of it 
probably corresponds to the Kansan, it is possible that a younger 
pre-Wisconsin drift may be represented. 
Geographical factor. The above descriptions of drifts pertain 
to deposits more or less distant from central New York. The 
diversity in the stratigraphy and topography of northern North i 
America introduces other considerations that may render these 
descriptions only partly applicable to other regions. Similarity 
of glacial deposits elsewhere may result only from identity, {a) in 
the stratigraphical terranes which furnished the debris; (h) in the 
period and conditions of weathering to which the debris was later 
exposed; (r) in the successions of ice-invasions; and {d) in the dis- 
tance of the sections being compared from the termination of ' 
the particular sheet in question. It is evident, therefore, that in | 
New England, New York, Pennsylvania and New Jersey specific | 
drift-sheets may have somewhat different features than have , 
been reported by investigators elsewhere. I 
TOPOGRAPHIC CONTROL OF THE EROSION AND DEPOSITION OF j 
DRIFT. j 
In general. It is probable that the main dissection lines of the | 
Finger Lake area even before the earliest glaciation were north- I 
[' 
R. D. Salisbury, Glacial Geology, Geological Survey of Ne-w Jersey, vol. v 
(1902), p. 174- 
Ibid,, p. 188. Ibid., p. 757. ^^Ibtd., p. 769. Ibid., p. 782. 
