﻿1848. LIGNITE BEDS. 193 



from the Rocky IMountain spur of Avhicli Clark's 

 Hill forms a portion, to the spur of which the hill 

 on the loAver side of the mouth of Great Bear River 

 is a prominent point, being directly across the 

 valley about twenty-five miles, but considerably 

 further by the course of the Mackenzie. The depth 

 to which the deposit descends below the bed of the 

 Mackenzie was not ascertained, but the height from 

 the surface of the water to the top of the bank 

 varies from ninety to one hundred and fifty feet. 

 Ten or twelve feet or more of the crest of the bank 

 consists of diluvial gravel with boulders, and the 

 soil is generally peaty to the depth of a foot or two. 

 The beds are usually almost horizontal or have a 

 very moderate inclination, but in some few places 

 they dip very considerably, and in the second reach 

 of the Mackenzie above Great Bear River a bed of 

 stone passes obliquely from the top to the bottom 

 of the clay bank. By the destruction of the coal 

 beds the cliff falls down, the slope is covered with 

 the gravel and boulders, and the latter pave the 

 channel of the river also. The strong current of 

 the river varies its direction from time to time, and 

 as the deposition or removal of alluvial islands ex- 

 pose or protect the banks, the debris of the ruined 

 cliffs accumulates or is carried away. This con- 

 stant waste of the bank would proceed much more 

 rapidly, were it not that the ground is still frozen 



VOL. I. o 



