No. 50.J 
439 
To understand this more fully, we may take for example any ol our 
shallow lakes or ponds, which are now being filled up by materials 
brought from the higher grounds, by freshets and the small tributary 
streams. 
While this state of things existed in the lower valley, nearly the 
same process was going on in the upper one. The fine materials 
brought down by the streams, were spread over the bottom, while the 
coarser were left on the margin, at the mouths of the inlets. The out- 
let by the Cashaqua, seems to have been early closed and another form- 
ed by wearing the chasm from Portage to Mt. Morris. During this 
period, the lake was drained to near the presenj; level of the river bed. 
The different and successive margins or shores of this lake are in many 
places clearly recognizable, but in others they are obhterated. The first 
opening for the water of this lake was from Portage, in nearly a direct 
line to Rogers' bridge, through a gorge now filled with alluvium. After 
the water was drained in this manner, from some cause, and probably 
the sudden drainage of a small lake at a higher level, a great accumu- 
lation of water occurred, which, carrying everything before it, swept 
down the alluvium, which completely blocked up the course of the 
stream, producing that immense deposit to the north of Portageville. 
The consequence of this catastrophe was the accumulation of water in 
the lake above, to such an elevation, that it found a passage over the 
surface along the present course of the river from Portageville to the 
Lower falls. The direction of the outlet being once given, the wear- 
ing process commenced and the result has been the production of that 
immense chasm in which are situated the three falls. The descent of 
water over these falls and intervening rapids, amounts to about 400 
feet. The perpendicular cliffs of rocks below the second fall are 350 
feet high. 
Here then, are two eras, clearly distinguishable, in which the diffe- 
rent portions of this gorge have been excavated, and both of them since 
the present configuration of the surface had become generally settled ; 
and long since that period, when the whole was submerged beneath the 
ocean. 
In the excavations in the alluvium now at progress at the north end 
of the tunnel at Portage, we find the first deposit somewhat regular, 
and consisting of materials in which those of northern origin form a 
part. This deposit appears to have been partially excavated and ano- 
