210 On the Geology of the Island of Montreal. 



a vertical and very thin sheet of trap. A drawing, made very 

 soon after meeting with this appearance, does not represent 

 any displacement of the calcareous strata ; and I well remem- 

 ber, that the union between the two layers or veins of trap is 

 perfect. 



In the quarry five hundred yards north of the race-course, 

 there is a vein eighteen inches thick, which is nearly horizon- 

 tal. It is only seen for a few feet. Dr. Lyons, Surgeon to the 

 British forces, an acute observer, to whom I am much indebted, 

 met with a horizontal vein, on the south flank of Mount Tra- 

 falgar, overlooking the priests' house. The west and north- 

 west parts of the base and sides of Montreal Hill, have not 

 yet been sufficiently examined ; but I do not look for much 

 information from thence, as they are employed in tillage, and, 

 as far as I know, have not been excavated for quarries, Sic. 



I shall now proceed to give some account of the limestone 

 overlying this trap, and receiving its ramifications. It is a 

 portion of the great basin of secondary rocks of North Ame- 

 rica, whose outlines have been ably traced by Dr. James, in 

 his account of the expedition to the Rocky Mountains, under 

 Major Long. A more detailed description of its line of junc- 

 tion with the elder and inclined rocks of the dividing ridge of 

 the vallies of Hudson's Bay, and the St. Lawrence, may be 

 found in Volume VIII. p. 77. of the American Journal of 

 Science. The particular form occurring in Montreal Island, 

 and overspreading nearly the whole of it, extends into Lake 

 Champlain and on the Richelieu on the south ; and northeast- 

 wards, down the St. Lawrence, as far as Cape Tourment, 

 thirty miles below Quebec. Its south east boundaries have 

 not been at all examined. We only know of the country south 

 of the St. Lawrence, below Montreal, that it abounds in 

 greywacke and clayslate, superincumbent on granite and 

 gneiss. Westerly and southwesterly, it unites with the lime- 

 stones of the Lakes, with which, if we are to judge by imbed- 

 ded minerals, organic remains, and geological position, it is 



