De Geer.] 
476 
May iS, 
vations, lias not quite filled it up, yet there appears to be no 
continuation of it on the other side of Long Island, even beyond 
the glacial deltas. 
This curious fiord-like shoaling of the submarine channel, be- 
fore it reaches the edge of the continental plateau, is repeated 
by the submerged river channels described by A. Lindenkohl 
from the Delaware and Chesapeake Bays. 
This phenomenon might perhaps be explained according to 
T. F. Jamieson’s suggestion for certain fiords, as a consequence 
of the unequal and intense subsidence of an iceloaded con- 
tinent. 
But concerning these channels, as well as the one described by 
Chalmers in the St. John River estuary and the large channels 
reported by Spencer from St. Lawrence Bay and several other 
places, we must allow that at present we know very little indeed 
of their history and precise age, with perhaps the general excep- 
tion that they may point to a high elevation in early glacial 
time. 
In this connection it is of interest that in America as well as 
in Europe the interglacial marine deposits at present accessible 
above the sea level are found only near the margin and at 
the outside of the region which during the last glaciation has 
been exposed to subsidence. I refer here to the interesting 
fossiliferous deposits described by Shaler, Upham, and others 
from Nantucket, Martha’s Vineyard, Long Island, and Boston. 
The question whether the Columbia formation belongs to the 
same subsidence cannot safely be discussed, before its marine 
origin is conclusively shown by fossils, boundary shore-lines, or 
other indisputable evidence. The same is true of the lower beds 
of sand and clay about 50 feet thick which Lyell in the report 
of his first voyage to North America describes from Beauport 
near Quebec. The clay with boulders, which he observed 
resting upon these beds and covered by fossiliferous, late glacial 
deposits, is as I could myself ascertain a true till, probably 
belonging to the last glaciation. 
Though the situation of these possibly interglacial deposits is 
open to the St. Lawrence estuary, their marine origin is very 
questionable, since no fossils have been found. 
But if it is difficult to get any idea of the interglacial geoid 
deformations from the marine deposits, it is still more so with 
