202 On the Geology of the Island of Montreal. 



organic remains (numerous and sometimes new and rare) un- 

 changed, although in contact with, imbedded in, and even 

 impregnating the trap.* 



The deposits which I have called alluvial, but which were 

 rather thrown down during the existence of vast inland seas, 

 after the last deluge, may lead to useful inferences from their 

 form and connexions, and from the nature and variety of their 

 contents. 



The fixed rocks of this district may be enumerated as fol- 

 lows : — A very compound trap constitutes the largest part of 

 Montreal Hill, and appears in great quantity in the plains on 

 its south. Besides emerging in the route of the Lachine Ca- 

 nal, a rapid visit enabled me to detect it in unstratified rock 

 masses, which just escape above the herbage, in the common 

 of La Prairie, a quarter of a mile west of the village, (six miles 

 from Montreal) a mile south of the parish church of Longueil, 

 (three miles east of Montreal) and on the banks of the St. 

 Lawrence, west of, and near the same church. It occurs in a 

 similar manner on the. river Richelieu, (twelve miles south- 

 east of Montreal) for one or two miles about Col. de Sala- 

 berry's Mills. Rolled fragments of this rock abound every 

 where in the large area included by the towns of Montreal, 

 Chambly, and St. John's, and extend southward at least 

 twenty miles above the foot of Lake Champlain, even to the 

 Genesee country, in a southwest direction, and up the St. 

 Lawrence, nearly as far as Prescott, in Upper Canada. At 

 the lower end of the Vaudreuil ferry, on the Lake of the Two 

 Mountains, the fragments of trap are so plentiful and angular, 

 (IS 19) that I suspect it occurs in place not far from thence. 



Near Montreal, the trap supports, and traverses in direct 

 contact, a conchiferous limestone, which floors nearly the 

 whole island, as well as can be ascertained, through its 



* Chambly Mountain, sixteen miles east by south, affords the nearest 

 primitive rock in place. 



