Association of American Geologists and Naturalists. 329 
rials in the southern drift. He was led to believe from the facts 
in the case, that there must be valleys of two distinct epochs. 
Prof. H. D. Rogers then addressed the meeting in a very elo- 
quent manner, showing how the absence of southern materials in 
the northern drift might be accounted for by supposing the forces 
of the northern currents to have been so great as entirely to have 
swept all vestiges of the superficial drift into the Gulf of St. Law- 
rence. This vast reflux of waters was attendant on the uplift of 
the continent, and the great drainage which resulted from the 
flowing off of the oceanic waters. 
Mr. Hall read a short paper in explanation of two sections at 
Portage, N. Y. 
Under the terms diluvium, drift, &c., are included products, which, 
however similar they may be in general characters, are often due to 
different causes, and are the results of eras widely separated in time, 
and differing in many essential circumstances. The more ancient ap- 
pear to have been the more universal, and as we descend to modern 
periods, the extent of the operation seems to have diminished. 
In our theories we have made provision for a wide sweeping deluge, 
for immense excavating waves, and for hemispheres of ice, but we have 
overlooked the subsequent and minor, though often important operations 
of the bursting of lakes, or the change in river channels, which must 
have occurred frequently during the earlier periods after the emergence 
of our continent from the ocean. The existence of such lakes, would 
be a natural consequence of the contour of the surface. 
Evidence of the outbreaking of such lakes is seen in the margins of 
all our great valleys, where more recent detritus is spread over the 
older deposits of that kind. , 
Bones, shells and fragments of wood, are frequently found in these 
deposits, which are referred to the drift period—though we are not pre- 
pared to say that the drift is destitute of such remains, yet those which 
Mr. Hall had seen were clearly in positions to be referred to a subse- 
quent period. 
In the excavation of the Genesee Valley canal, at Portage, along the 
side of a hill which consists of alternating layers of fine sand and clay, 
at a point about two hundred feet above the base of this deposit, some 
fragments of fine-grained wood, highly impregnated with iron pyrites, 
were found. This was in a layer covered by a mass of gravel and sand 
eighty feet thick, which, from the nature of its materials, was a deposit 
subsequent to the drift, and of southern origin.* 
* The existence of these two deposits was pointed out in the Annual Geological 
Report for 1839. 
Vol. xiv, No, 2.—July-Sept. 1843, 42 
