386 
THE GEOLOGIST. 
locks and railway bridges. The beds abound with the remains of encri- 
nites and cystidians, and these give to the rock a crystalline texture which 
constitutes one of its valuable cliaracters. The stones from Pointe Claire 
and Cornwall belong to the Bird's Eye and Black Eiver formation. They 
are black, compact, and thick-bedded. The Trenton formation, which is 
next above the " Bird's Eye and Black River," yields excellent building- 
stone at Montreal, at Chevrotiere, and many other places. The best stone 
in Montreal is from a ten-feet band of grey bituminous limestone near the 
base of the formation, and which is a mass of comminuted organic remains 
consisting largely of the ruins of crinoids and cystidians. The best houses 
in Montreal are built of this stone. The strata in the neighbourhood of 
that city are much traversed by trap dykes, which have probably a connec- 
tion with an intrusive mass extending over seven hundred acres, and con- 
stituting Mount Royal, from which the city and the island take their names. 
The Niagara formation, the equivalent of our Middle Silurian, produces 
a beautiful and enduring dolomite at Owen Sound. A rather more com- 
pact dolomitic stone comes from the lower part of the Niagara formation 
at Noisy Clear Falls, Nottawasaga. Another excellent specimen is shown 
from Rookwood, Eramosa. The Guelph formation extends over a large 
area, and much of the rock is of the same character as the specimen in the 
collection from the thriving town of Guelph, where the quarries expose 
about 15 feet of light grey crystalline dolomite ; easily worked, it is 
suitable for the best architectural purposes, and appears to be very durable. 
But Oxbow, on' the Saugeen River, furnishes the best dolomite for fine 
architectural purposes which has yet been discovered m Canada. It 
resemble^ Caen stone in the facility with which it can be worked ; but it 
is closer-grained and by no means so absorbent. There are two bands of 
stone there, each about 10 feet thick, in the upper part of the Onondaga 
formation ; the above is from the upper band : the lower band has a very 
light grey oolitic bed, 17 inches thick, that is much used for supporting 
water-wheels in mills in the neighbourhood, and is found to answer well, 
becoming highly polished under the action of a revolving shaft. Lyn, 
Elizabethtown, Nepean, Grenville, Quin's Point, furnish specimens of the 
Potsdam sandstone, which constitutes the summit of the lowest group of 
fossiliferous rocks in Canada. At Lyn the massive beds of that formation 
are seen resting on Laurentian gneiss. Amongst other samples are, from 
Pembroke, a fine freestone from the Chazy beds ; from Hamilton, Burton, 
a fine-grained sandstone, 10 feet in thickness, the " grey band " of the 
Medina formation (Middle Silurian) ; from Georgetown, Esquesing, and 
Nottawasaga, a hght-grey freestone, 20 feet thick (Medina "grey band") ; 
and from North Cayuga a white sandstone belonging to the Oriskany for- 
mation (Devonian), which runs through Haldemancl county in Lower Ca- 
nada. From Abercrombie, labradorite from the Laurentian formation ; it is 
of the opalescent variety, which occurs in cleavable masses in a fine-grained 
base of the same mineral, composing mountain masses. When these are 
thickly disseminated in the paste, the stone becomes a beautiful decorative 
material, applicable to architectural embellishment and articles of furni- 
ture. Its hardness is about that of ordinary feldspar, and it would in 
consequence be moi'e expensive to cut and polish than serpentine or 
marble, but it is not so readily scratched or broken, and would therefore 
prove more lasting. Professor Emmons states that a block submitted to the 
action of a common saw used in sawing marble, moved by the waste power 
of a common water-mill, was cut to the depth of 2 inches in a day, which 
is understood to be one-fifth the amount that would be cut in a block 
of good marble in the same time. It would thus appear, that though the 
