OF CENTRAL CANADA PART V. 339 



which retain their original sedimentary aspect, and occur, for the 

 greater part, in undisturbed beds. It extends along both sides of 

 the St. Lawrencs from the western boundary of the Province to the 

 neighbourhood of Quebec. In the west, it includes the counties of 

 Vaudreuil and Soulanges, lying in the point of the triangular space 

 immediately west of the junction of the Ottawa and St. Lawrence- 

 Rivers. From the county of Vaudrouil, its northern boundary 

 crosses the Ottawa, and then, keeping entirely on the north side of 

 the St. Lawrence, runs along the southern edge of the Laurentide 

 district already described, and gradually approaching the river, 

 strikes it a short distance below Quebec. Its southern limit runs 

 from the south-west corner of Huntingdon (south of the St. Law- 

 rence), along the boundary-line between the Province and the State 

 of New York, to a little beyond the River Richelieu at the northern 

 extremity of Lake Champlain ; and east of this, the district is 

 bounded by the disturded and metamorphic area of the Eastern 

 Townships its actual limits in this direction being a remarkable 

 line o^f dislocation, with accompanying fault, running (as first traced 

 out by Sir William Logan) from near the north-east end of Lake 

 Champlain to the vicinity of Point LeVis, and from thence, by the 

 City of Quebec, along the north side of the Island of Orleans, and 

 down the river and Gulf, between the Island of Anticosti and the 

 Gasp^ shore. 



The rock-formations of the district belong to three distinct series, 

 namely : stratified Palaeozoic formations ; eruptive rocks ; and 

 Glacial and other Post-Cainozoic deposits. The stratified rocks, pro- 

 per, consist of representatives of the Potsdam, Calciferous, Chazy, 

 Black River and Trenton, Utica, and Hudson River formations 

 with some small exposures, south of the St. Lawrence, of strata re- 

 ferred to the Medina group ; and a few outlying patches of Upper 

 Silurian strata (belonging to the Lower Helderberg formation) in 

 the vicinity of Montreal. These formations are broken through in 

 places by large eruptive masses of trachytic and trappean rock, 

 forming a series of picturesque mountains, which rise abruptly from 

 the generally level surface of the district in the more southern and 

 western portions of its area ; and in addition to these Palaeozoic and 

 Eruptive rocks, Glacial and Post-Glacial accumulations, with deposits 

 of comparatively modern origin, occur throughout the district 

 generally. 



