28 The Ottawa Naturalist. [April 



Rouge River, but below this place the hill rang'e trends off more 

 to the north-east and a broad plain occupied partly by sand and 

 largely by clay, extends southward to the St. Lawrence. The 

 northern part of this area is treversed by the North River, which 

 between St. Jerome and the town of Lachute has but little current 

 and follows a westerly course till the latter point is reached when 

 it bends abruptly to the south and meets the Ottawa near the 

 village of St. Andrews, near the upper end of the Lake of Two 

 Mountains. 



To the south of the North river and east of Lachute a rock 

 ridge formed of the Potsdam and Calciferous rocks comes in and 

 extends eastward for some miles. South of this a broad well 

 terraced valley extends across to the lower portion of the Ottawa, 

 but this area is again traversed by a granite ridge which 

 rises just to the east of St. Andrews and extends eastward for 

 four to five miles. Between these two ridges the depth of clay 

 and gravel is great. At one point several borings have been 

 made, one ot which reached a depth of over 120 feet without 

 touching the underlying rock, so that the bottom of this old 

 channel is many feet below the present level of the river. 



On the south side of the Ottawa below Ottawa city, the 

 country between the river and the St. Lawrence is generally level 

 or broken by low ridges, sometimes of rock but often of gravel or 

 boulders which have come from the north side of the Ottawa. 

 Over a large part of this area great deposits of clay, overlaid in 

 places by sands and gravels, are seen, and a peculiar feature of 

 these deposits is noted in the fact that while the clays are undoubt- 

 edly of marine origin they rarely show marine fossils, while the 

 overlying sands and gravels contain these in immense quantities 

 at very many places. These marine shells however apparently 

 cease west of a line drawn from Smith's Falls to Prescott or have 

 not yet been noticed in the western area, though there is no 

 apparent break in the character of the surface deposits in this 

 direction. 



South of the Ottawa also the evidences of an old river channel 

 are very clear. A large number of borings have been made in the 

 last half dozen years both in the vicinity of the river itself and in 

 the area to the south. Some of these are in ^he course of the east 



