On the Geology of the Island of Montreal. 211 



cotemporaneous. The compact form is not to be distinguish- 

 ed from that of the north east end of Lake Ontario ; serving 

 as the substratum for the adjacent parts of the State of New- 

 York and Upper Canada. 



The limestone of Montreal Hill is bluish black or bluish 

 brown, without lustre, fine-grained passing into compact, 

 easily scratched by steel, and of conchoidal fracture when free 

 from shells. When exposed to the weather, it is divided into 

 horizontal layers, from six to twenty-four inches thick, some 

 of them containing silica in chemical combination (with in- 

 creased hardness) ; and others chertz in horizontal bands. 

 How thick the strata are, at some depth beneath the surface, 

 is very doubtful. This form of the limestone is well seen at 

 McTavish's Tomb, on the west road to St. Catharine's, and 

 on the north of the hill at the base : every where full of the 

 organic remains of the level country. The limestone of the 

 race-course, so traversed by dykes, is in all respects similar to 

 that of the hill. 



The small quarries scattered over a field north east of the 

 race-course, and often alluded to already, are nearly on the 

 same level with those of the latter spot ; but are perhaps two 

 feet lower. They are only opened to the depth of nine feet of 

 rock. Of this, the upper third is a brown, knotty, disinte- 

 grated, calcareous shale, greatly charged with iron in the 

 brown carburet and pyritic forms. The lower two thirds, by 

 rapid, but not abrupt transition, consist of layers of bluish 

 gray and grayish brown limestone, from eight to thirty inches 

 thick. These are highly crystalline, in shining rhomboidal 

 facettes, which average one-sixth of an inch in diameter, and 

 display no trace of organization. Williams's Quarries pre- 

 sent the same appearances as these. 



The limestone on the north of the island, in the quarries and 

 broken platforms along the Riviere des Prairies, is nearly the 

 same as the crystalline species of the quarry adjacent to the 

 race-course. The organic remains are the same, but where I 



