000 Extracts from the Minute Book of the Geological Society . 
the bank cannot be less than 150 feet high. Here there appears 
to have been at some former time an extensive slip. The fallen 
mass is about twenty or thirty yards wide, and two or three 
hundred yards long, and when I observed it, was about 10 or 12 
feet higher than the river, which was then much above its ordinary 
level. Timber grew upon this under-cliff to a pretty good size, 
as the earth on its surface was deeper than upon the summit of the 
bank, where the layer of vegetable mould was very thin. 
Near the first rapid as you ascend the river the acclivity of 
the bank is about 60°; in many places the ascent is almost 
perpendicular; an instance of very great tenacity and consistence 
in a body containing a large proportion of sand with scarcely any 
mud. The substance of the bank, when consisting almost entirely 
pf clay, not unfrequently assumes the appearance of stone, having 
the form of regular lumps, which resemble limestone. These 
lumps break under pressure, but in breaking preserve an angular 
shape, the surfaces of the fracture resembling those of limestone. 
Limestone is found a few feet below the clay at the bottom of 
the bank and in the bed of the river. 
At the second rapid as you ascend the river, the portage is good, 
being about 100 yards in length, over flat limestone rocks, which 
are not more than four or five feet above the level of the water. 
From the head of this rapid the distance is two miles to the foot of 
the great limestone fall. 
At the great limestone fall, the river, which is here nearly a 
mile broad, does not fall suddenly, but rushes with inconceivable 
impetuosity over the beds of limestone. We had here an op- 
portunity, in walking over the surface of the ice, to notice the 
tremendous height to which the water had risen during the spring 
floods at these rapids, trees of various sizes lying broken down by 
