Geology of the Monlmorenci — Emmons. 97 
amine those below. The first I shall speak of is the one forming the 
great fall. This is rather a fine grained gneiss, and furnishes from some 
portions of it, carbonate of copper, which stains the sandstone alread 
noticed. It rises in a perpendicular ledge, and stretches in an unbroken 
uniform mass entirely across the gorge. It is a naked wall, two hundred 
and forty feet high, and serves by its great mass, as seen below, to add to 
the magnificence of the scene. 
Against this ridge of gneiss, the black slate of the Hudson river series 
reposes. Viewed from above, it appears at the first sight to rest upon 
the gneiss conformably-; but upon a close inspection it will be seen that 
it is in a nonconformable position; the strata of slate are less inclined 
than those of the gneiss, and the whole arrangement finally appears to 
result from a derangement of the masses. But we have in this place 
several sedimentary rocks of different ages, nearly if not quite in contact, 
resting upon the primary mass, and it might be quite puzzling to deter- 
mine which is the oldest'mass, the rocks above the fall or the slate below, 
as both rest vipon the primary unconformably, and only a few years since 
the slates were placed in the geological systems upon the primary in the 
precise position which it here occupies. 
The annexed diagram will serve to explain more clearly the relations 
of the rocks at the fall. 
From the facts which have been given, and from an inspection of the 
diagram, it will probably be conceded that there is at the fall of Mont 
morenci a fault, or uplift on one side, by which the horizontal masses 
have been elevated, and a down-heave on the other, by which the slate 
has been thrown into an inclined position; for an uplift simplv would 
have fractured and elevated the strata, but would have left the slates in 
their original horizontal position, or perhaps, instead of giving the whole 
mass an inclined position, would have merely bent their edges. Such a 
result is not uncommon. 
An inquiry may be raised at this stage of our examination, if the Black 
Slate really occupies a position upon and above the Trenton, why is it 
not to be found still in place.'' The answer to this question is at hand;, 
the entire mass of slates, shale and sandstone which constitute the graj-- 
wacke of authors is entirely swept off. The force from beneath which 
produced this remarkable uplift, shattered and broke the mass of shales, 
&c , so that they were exposed to the full force and power of floods and 
currents of water which have swept over the earth at different periods of 
its history. We are justified also in bringihg to our aid the transporting 
power of icebergs, agents whose effects and power have been admitted 
by the most learned an.l able geologists in Europe and in this country. 
That this answer or conjecture is more than probable will be shown in 
the final report of the Second Geological District, the details necessary 
to establish such a result not being admissible in the present number of 
this magazine. 
But to return to the consideration of the fault or uplift which produced 
the fall of the river at this particular place; we are not to suppose that 
