10(5 



stones occurs, which has a very considerable extent. In places the soil 

 and thin forest growth has been removed and the rounded stones are 

 laid bare sometimes over a space of several acres. These shew low 

 terrace like ridges of eight or ten feet high, the whole deposit sloping 

 towards the valley of the Riviere a la Graisse which flows past the 

 northern flank of the mountain. The rocks comprising this curious 

 deposit, which is known locally as the Devil's Field, are nearly all of 

 reddish syenite often composed almost entirely of red felspar, with 

 others of flesh-red felsite and porphyry, and a few of quartzite, the latter 

 belonging presumably to some portion of the Laurentian, which is found 

 on the north side of the Ottawa River. The bulk of the syenite and 

 felsite rock is from the mass of Rigaud mountain itself. This deposit 

 extends for several hundred yards along the north face of the moun- 

 tain, and has a depth of from ten to twenty feet, though the bottom has 

 not apparently been reached, but lower down the mountain side the 

 deposits become finer, being largely coarse gravel and sand. There is every 

 probability that this curious deposit marks an old shore or beach of the 

 time subsequent to the glacial period. The locality has been briefly 

 described in Geo'l. Can. 1863, p. 896; and is well worthy a visit from 

 any one interested in the subject of glacial geology. 



That the surface of the country was below the sea level at this 

 period is clearly shewn by the presence of marine shells in extensive 

 deposits of blue clay which is widespread throughout the valley of the 

 Ottawa River. Along the streams flowing from the north, as the 

 Rouge, l)u Lievre, Gatineau, etc., it has been recognized for nearly 

 100 mile from their juncture with the main stream Frequently the 

 clay deposits are covered by a mantle of sand often of considerable 

 thickness. That the greater part of these clays are of marine origin is 

 shewn by the finding of marine shells at elevations of 450 and 500 feet 

 above present sea level at various points throughout the area. Along 

 most of the rivers throughout this section a succession of terraces occurs, 

 some of which along the upper part of the Rouge River are 1000 

 feet above the sea level. 'The distiibution of the clays and sands 

 throughout the northern area is very extensive ; great areas as the 

 ka/ubazua plains embracing many square miles on which the soil is nearly 

 pure sand, the vegetable growth consisting of small pine and blueberry 



