94 GEOLOGICAL AREAS OF CANADA. 



especially mentioned — are distributed more or less generally throiigii- 

 out the region. The glacial striae of the district run most commonly 

 either towards the south-east or south-west ; but in some few localities 

 their direction is almost north-and south, and in others, not far 

 removed from east-and-west. 



(2.) The Upper St. Lawrence District. — This is essentially a Silurian 

 area, occupied — apart from some isolated eruptive-masses — by sand- 

 stones, limestones, and other strata, which retain their original 

 sedimentary aspect, and occur, for the greater part, in undisturbed 

 beds. It extends along both sides of the St. Lawrence from the 

 western boundary of the Province to the neighbourhood of Quebec. 

 In the west, it includes the Counties of "Vandreuil 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 Vandreuil, 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. Lawrence), 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 disturbed and 

 metamorphic area of the Eastern Townships — its actual limit in this 

 direction being a remarkable line of dislocation, with accompanying 

 fault, running (as first traced out by Sir William Logan) from near 

 the north-west end of Lake Champlain to the vicinity of Point Levis, 

 and from thence around the City of Quebec, along the north side of 

 the Island of Orleans, and down the river to near the mouth of the 

 Magdalen, where it enters and runs along the Gaspe shore. 



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

 The stratified rocks, proper, consist of representatives of the Potsdam 

 Calciferous, Chazy, Black River and Trenton, Utica, and Hudson, 

 River (Lower-Silurian) formations — with some small exposures, south 

 of the St. Lawrence, of strata referred to the Middle Silurian, 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 



