﻿124 GEOLOGICAL STRUCTURE JuLr, 



hundred and twenty to ome hundred and thirty 

 feet high, resting on limestone whose beds are un- 

 dulated in two directions. The limestone is imme- 

 diately covered by a thin stratum of a yellowish- 

 white earth, which, from the fineness of its grain, 

 appears at first sight to be a marl or clay. It does 

 not, however, eff*ervesce with acids, is harsh and 

 meagre, and, when examined with the microscope, 

 is seen to be chiefly composed of minute fragments 

 of translucent quartz, with a greyish basis in form 

 of an impalpable powder. This seam follows the 

 undulations of the limestone ; but the beds of the 

 superincumbent bituminous shale, or rather of sand 

 charged with slaggy mineral pitch, are horizontal. 

 About thirty miles below the Clear-water Kiver, 

 the limestone beds are covered by a bituminous 

 deposit upwards of one hundred feet thick, whose 

 lower member is a conglomerate, having an earthy 

 basis much stained with iron and coloured by 

 bitumen. Many small grains and angular frag- 

 ments of transparent and translucent quartz com- 

 pose a large part of the conglomerate, which also 

 contains water- worn pebbles of white, green, and 

 otherwise coloured quartz, from a minute size up 

 to that of a hen's egg, or larger. Pieces of green- 

 stone, and nodules of clay-ironstone, also enter into 

 the composition of this rock, which, in some places, 

 is rather friable, in others, possesses much hardness 



