844 The American Geologist. May, 1892 
Annual Report, for 1890, by N. H. Winchell. pp. 255 with illustrations. 
Minneapolis, 1892. 
IT. Proceedings of Scientific Societies. 
The Journal of the Cincinnati Society of Natural History, Vol. xiv, 
Nos. 3 and 4 contain: Manual of the Paleontology of the Cincinnati 
Group, by Jos. F. James; Description of some Subcarboniferous and 
Carboniferous Cephalopoda, by 8. A. Miller and Chas. Faber. 
Proceedings of the Philadelphia Academy of Natural Sciences, 1891, 
Part 111 contains: Notes on some little known American Fossil Tor- 
toises, by Dr. G. Baur; A new Meteoric iron from Garrett Co., Md., by 
A. E. Foote; Preliminary Notice of some Minerals from the Serpentine 
Belt, near Easton, Pa., by John Eyerman. 
CORRESPONDENCE. 
THe DELTAS OF THE Monawk.— Pending further investigation, per- 
mit me to make the following brief preliminary statement relating to 
observations bearing on the origin of the terraces of the Mohawk valley 
and the Iroquois beach. 
The terraces of the Mohawk valley are strongly developed, especially 
along its north or Adironack side. Each terrace is associated with some 
tributary of the Mohawk. More and longer streams enter from the 
north than the south, and they tlow down steeper slopes and have greater 
transporting power. Each terrace is built up about the mouth of a 
stream in the form of a delta,as though the stream had entered a lake 
or estuary of still water. In a few instances where there is a consider- 
able distance between the larger tributaries there is no terrace. In 
general, the magnitude of the terraces appears to be proportional to the 
size of the streams which made them. The long heavy terrace below 
Herkimer appears to be the delta of Canada creek, which is the largest 
tributary from the north. This great deposit choked the Mohawk valley 
from side to side for a considerable distance, and was probably the 
agent which turned the river out of its old bed and forced it over the 
rocky ledge at Little Falls a few miles below. 
If these terraces are in fact deltas, then the water in which they were 
made must have been either a lake or a marine estuary. Prof. Merrill 
has already described estuarine deltas along the Hudson from New York 
city to Fishkill, rising toward the north, and then again at Albany and 
Schenectady at an altitude of 340 feet. If the old Hudson marine estu- 
ary reached Albany it was. probably continuous with the post-glacial 
submergence of the Champlain basin. In this event it is hard to see 
how the Mohawk valley could have escaped being a marine estuary also. 
If it was, then the great deposits near Albany can hardly have been 
made by the Mohawk, but are probably the delta of the upper Hudson, 
This explanation comports best with the delta-form terraces of the Mo- 
