﻿1848. 



GllAVEL BEDS. 189 



were on fire near Bear River, when Sir Alexander 

 Mackenzie discovered them, in 1785, and the smoke, 

 with flame visible by night, has been present in 

 some part or other of the formation ever since. 



Fi'om one to four beds of coal are exposed above 

 the water level on the banks of the river, the 

 thickest of which exceeds three yards, and was 

 visible a short way above Bear Kiver in the 

 autumn only, — the Mackenzie being then seven or 

 eight feet below its spring level. 



Interstratified with the coal beds, there are 

 layers of gravel which occasionally, through the 

 intermixture of clay more or less iron-shot, ac- 

 quire tenacity enough to form vertical cliffs, but 

 more often are very crumbly. The pebbles com- 

 posing the gravel vary in size from that of a pea to 

 that of an orange, and are formed of Lydian-stone, 

 flinty slate, white quartz, quartzose sandstone and 

 conglomerate, clay-stone, and slate-clay. The gravel 

 is sometimes seamed by thin layers of fine sand, 

 and its beds vary in thickness up to thirty or forty 

 feet. 



In place of the gravel, a friable sandstone is often 

 interposed between the coal beds or rests upon 

 them. It is fine-grained, often dark from the dis- 

 semination of bituminous matter, and has so little 

 tenacity, that in many places it is excavated by 

 the sand-martens. Being porous, it fills with 



