386 



THE GEOLOGIST. 



locks and railway bridges. The beds abound witli the remains of encri- 

 nites and cystidians, and these give to the rock a crystalline texture which 

 constitutes one of its valuable characters. 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 E,iver," 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 Boyal, from which the city and the island take their names. 



The Niagara formation, the equivalent of our Middle Sikirian, 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 ISToisy Clear Falls, NottaM^asaga. Another excellent specimen is shown 

 from Rookwood, Eraraosa. The G-uelph 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 Hiver, furnishes the best dolomite for fine 

 architectural purposes which has yet been discovered m Canada. It 

 resembles 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 tldck, 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, JSTepean, 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 G-eorgetown, Esquesing, and 

 Nottawasaga, a light-grey freestone, 20 feet thick (Medina "grey band") ; 

 and from North Cayuga a white sandstone belonging to the Oriskany for- 

 mation (Devonian), w^hich runs through Haldemand 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, a])plicable to architectural embellishment and articles of furni- 

 ture. Its hardness is about that of ordinary feldspar, and it would in 

 consequence be mo]*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 connnon saw used in sawing marble, moved by the waste power 

 of a connnon 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 



