62 



sumed their present character. Such a change of circumstances from those, 

 cxistiog during the deposition of the Treutou formation also led to a change in 

 til fauaa of these Utica Seas ; the GrajitoUtes, whicli in olden times had swarmed 

 the seas, during the deposition of the Calciferous and Chazy, now finding a suit- 

 able habitat returned in such abundance that the presence of these fossils may be 

 considered a chief characteristic of tliis formation. Trilobites also, of forms 

 diverse from thosa of the Trenton now made their first appearance in these turbid 

 waters. It is no doubt owiug to the great prevalence of these two types of life 

 in that period of the earth's history that the rock owes its bituminous character. 



This change which occurred at the close of the Trentoa, was at first quite 

 gradual, for, as may be clearly seen, the upper strata of that formation are for the 

 most part separated from each other by thin bands of shale and artjillaccous 

 schists, indicating the oscillatory movements which then begun, foretold the 

 complete disruption in the northern seas. 



CHEMICAL COMPOSITION. 



Several careful analyses of the rocks of this formation have been nude by 

 Messrs. Chandler & Kimball for Prof. Whitney, who have published them in the 

 Geology of Wisconsin, and mention of which is made in the Geology of Canada, 

 18G3. Of these analyses, chiefly of specimens from various parts ot Canada, one 

 from the Gloucester beds, in this neighbourhood, is noticed as yielding an 

 especially large percentage of magnesia. The dolomitic nature of these beds is 

 further shown by the appearance of their weathered surfaces, which assume a 

 brownish-yellow colour. 



Very little can be said a^ to the existence of minerals in these rocks, for they 

 are so few, and, with the exception of bitumen, there are none of any importance. 

 The occurrence, however, of a considerable percentage of this mineral in the 

 shale at Collingwood, induced a company some few j'ears ago, to start operatioas 

 and extract the oil ; but before much was accomplished the discovery of the same 

 mineral in much greater abundance in the Hamilton shales, of Devonian 

 age, caused the operations at Collingwood to be suspended ; these, however, may 

 prove of considerable value at some future date. 



At the village of Windsor there is also said to be a valuable deposit of 

 bitumen belonging to the Utica Slate. Other minerals occur sparingly, as iron 

 pyrites {pyrite or marcasite) which is generally found replacing entirely or lightly 

 coating fossils, particularly trilobites and ort/ioceratites. Selenile, or the 

 hydrated sulphate of lime, also occurs in fine scales di.sseminated over the divis- 

 ional planes of the strata, or, partly coating organic remains. 



GEOLOGICAL DISTRIBUTION. 



The remarks made will be in special reference to Canada ; but in tracing out 

 the belt along its line of outcrop, it will, of course, be necessary to notice parts 

 of the United States. Beginning then with the deposit in its most easterly ex- 

 tension, it is found occurring near the mouth of the Ste. Anne Eiver, Montmor- 

 cnci, P.Q., where a portion of the rock exposure there shows 318 feet in thick- 

 ness of Utica Slate. Proceeding thence in a westerly direction it forms a belt, 

 at times interrupted, along the northern shore of the St. Lawrence, with a general 

 south-easterly dip, sometimes concealed beneath the waters of the river, at other 

 times cropping out at the summit of various anticlinais and on the superior axes 

 of disturbed areas, whilst large tracts of it lie hid beneath the soil or drilt. Thus, 

 the belt proceeds till it reaches the city of Montreal, where several exposures 

 can be seen on the Mountain side, ac St. Helen's Island, Point St. Charles, and 

 other places in that locality, the rock being much altered and hardened on account 

 of the numerous plutonic dykes that traverse it. Hence the belt bends to the 

 south-east, and then again to the south till it reaches Lake Champlain, where the 

 formation can be traced beneath the w.iters of the lake by means of the islands 



