Geology of the Montmorenci — Emmons. 99 
they agree with what has been published by English geologists of the 
Cambrian rocks, leaving of course out of view the lower portions of this 
system, which are either those of shales in an altered state, or else are 
the true primary. The suggestion contained in these remarks that the 
Cambrian rocks are really a portion (but not the lowest portion) of the 
Silurian, has been a conviction of my own mind for a long time, and I 
find that others entertain the same views. 
It is a conviction which has been gaining ground with the progress of 
discover^', but which has not resulted from any single discovery of itself. 
But it is proper to notice here one souree of difficulty in regard to the 
rocks of Hudson river, especially on their eastern border. It is the fact 
of their overlapping in this direction, the Trenton limestone and the other 
transition rocks beneath. The consequence has been that, in traveling 
from east to west, or from Massachusetts and Vermont to New York, we 
pass directly from the primary mass to the higher members of the transi- 
tion system, consequently they have placed them upon the primary, and 
considered them as the lowest of the transition ; whereas, there intervenes 
between these Hudson river slates and primary, the Trenton limestone 
Birdseye, Calciferous, and Potsdam sandstone, the aggregate thickness of 
which exceeds a thousand feet. Not one of the lowest members of the 
transition'system appears in the eastern prolongation between the High- 
lands of the Hudson and the Highlands north of Quebec, adjacent to the 
primary, in consequence as has already been said, of the overlapping of 
those rocks formerly termed graywacke, or now known as the Hudson 
river series. There are two other difficulties which have served to per- 
plex and confuse geologists, viz.: the striking mineralogical character of 
some of the masses of the Hudson river series, to the talcose slates of the 
primary, and also the great correspondence in kind and amount of their 
dip. 
I am not able for want of space to speak of these difficulties. It is 
evident, however, that the slates and shales do not conform to the pri- 
mary, they rather rest against the primary, and though in both the dip is 
to the east, still the constant dip of the slates is less than in the primary. 
There is a fact which is worth pursuing and which has some bearing 
upon this question, that is the slates of the Hudson river and lake Cham- 
plain are placed between two different mountain systems — the ranges, 
north of the Mohawk valley, all of which clearly compose one system^ 
and the Green mountains which is another. The force which may have 
served to produce one or the other of these systems may have caused 
this remarkable derangement in the slate system, producing at the period' 
■of their elevation the derangement called a downheave. The known 
facts, however, are not sufficient to establish the mode and manner in, 
which these border rocks as they may be termed, (meaning the slates 
and shales), were deranged. They are not of great thickness where thev 
are horizontal, but when inclined, they appear to be immensely thick.. 
In crossing the formation, for example from east to west, it is apparently 
20 or 25 miles thick, for as yet it has been impossible to recognize the- 
