§^ THE CANADIAN NATURALIST. [Vol. vi. 



lines loaded with boulders, or " ozars." Most of them convey to 

 my mind the impression of ice-action along a slowly subsiding 

 coast, forming successive deposits of stones in the shallow water, 

 and burying them in clay and smaller stones as the depth in- 

 creased. These deposits were again modified during emergence, 

 when the old ridges were sometimes bared by denudation, and 

 new ones heaped up." 



" I conclude these remarks with a mere reference to the alleged 

 prevalence of lake-basins and fiords in high northern latitudes, as 

 connected with glacial action. In reasoning on this, it seems to 

 be overlooked that the prevalence of disturbed and metamorphic 

 rocks over wide areas in the north is one element in the matter. 

 Again, cold Arctic currents are the cutters of basins, not the 

 warm surface-currents. Further, the fiords on coasts, like the 

 deep lateral valleys of mountains, are evidences of the action of 

 the waves rather than of that of ice. I am sure that this is the 

 case with the numerous indentations of the coast of Nova Scotia, 

 which are cut into the softer and more shattered bands of rock, 

 and show, in raised beaches and gravel ridges like those of the 

 present coast, the levels of the sea atthe time of their formation." 



2. The Leda Clay. 



This deposit constitutes the subsoil over a large portion of the 

 great plain of Lower Canada, varying in thickness from a few feet 

 to 50 or perhaps even 100 feet in thickness, and usually resting 

 on the Boulder clay, into which it sometimes appears to graduate, 

 the material of the Leda clay being of the same nature with the 

 finer portion of the paste of the Boulder clay. Its name is de- 

 rived from the presence in it of shells o^ Leda truncata, often to 

 the exclusion of other fossils, and usually in a perfect state with 

 both valves united. 



The Leda clay in its recent state is usually gray in colour, 

 unctuous, and slightly calcareous. Some beds, however, are of a 

 reddish hue ; and in thick sections recently cut, it can be seen to 

 present layers of different shades and occasional thin sandy bands, 

 as well as layers studded with small stones. It sometimes holds 

 hard calcareous concretions, which, as at Green's creek on the 

 Ottawa, are occasionally richly fossiliferous, but more usually are 

 destitute of fossil remains. When dried, the Leda clay becomes 

 of stony hardness, and when burned it assumes a brick-red colour. 

 When dried and levigated it nearly always affords some foramin- 

 ifera and shells of ostracoids ; and in this as well as in its colour 



