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231 
the agent which has thus rent the solid earth and torn apart the strong- 
est plates which encircle it. 
The examination of this chasm will also show us how, after the rent 
is made, the materials necessarily broken up may be removed by a 
powerful current of water, by which the breach will increase in width 
until it becomes a deep valley, bounded by an escarpment more or less 
abrupt. 
Some valleys in St. Lawrence county, seem to have been formed in 
this way. The cracks or rents pursue uniformly a given course, with- 
out turning much to the right or left. In many instances, undoubted- 
ly, the course of rivers is determined by these rents and fissures, and 
circumstances may so modify them that they may become the sites of 
long narrow lakes, similar to Lake Champlain. A stratum elevated by 
an upheave will probably attain a greater elevation along the line where 
the greatest force operated, and from this line it will dip like the roof 
of a house; the line of greatest elevation would suffer a fracture. An 
extensive removal of the ruins of such a stratum might form the channel 
of a river or the site of a lake. The dip of the rocks on the shores of 
the Champlain, and on the banks of the St. Lawrence river, is such, 
that the bed of one and the channel of the other may have been formed 
in a way analagous to the one here suggested. 
In concluding my remarks on the transition rocks of St. Lawrence 
and Essex, I consider it proper to add the following: 
1st. The whole series evidently belong to the grauwacke group of 
European authors. One of the members of this group, however, is more 
developed here than in Europe, or even in any other section of our own 
country; this is the sandstone just described. That it is a distinct, se- 
parate and independent stratum, cannot be doubted by any one who 
will examine it in St. Lawrence and Essex counties. It is true that 
it passes into the calciferous sandrock; still the sandstone without a par- 
ticle of lime is as extensive as the calc. sandrock of Eaton, and so far 
as I have observed never alternates with it, but is always beneath. 
2d. The relative position of the whole grauwacke series is exhibited 
to great advantage at Port Kent and Burlington, Vt. To show this I 
have introduced a wood cut, (fig. 16,) which embraces the sandstone of 
