﻿1848. SHALY BEDS. 177 



that have dropped from above pave the beach in 

 many places as closely and regularly as if it were a 

 work of art, the passage of ice over them driving 

 them firmly and evenly into the bed of tenacious 

 clay which the shale in breaking down produces. 



I have no evidence whereby the geological age 

 of the shale may be certainly deduced, but am 

 inclined to consider it as belonging to the epoch of 

 the Marcellus deposit, on account of its exact 

 lithological resemblance to the bituminous beds of 

 Athabasca River, and the occurrence of the Tenia- 

 culites jissurella in the fragments which line the 

 beach at the west end of Great Slave Lake.* The 

 difficulty of deciding upon the age of the beds 

 through which, the river flows is increased by the 

 occurrence among them of a tertiary lignite form- 

 ation, which also takes fire spontaneously. This 

 general account of the rocks of the Mackenzie is 

 here introduced to facilitate the subsequent de- 

 scriptions of such points as I landed upon. 



With respect to some of the more remarkable 

 quadrupeds that inhabit the Rocky Mountains, I 



* In 1826, Ml". Sowerby referred some fossils which I 

 obtained from the limestone beds of the Mackenzie, to the 

 Oxford oolite and cornbrash. These, which were mostly 

 terebratulites, are not now within my reach, but should his 

 opinion be confirmed by further specimens from the same 

 quarter, they would indicate that the bituminous shale of the 

 Mackenzie belongs to the lias. 



VOL. I. N 



