CH. vii. ORIGIN OF BOULDEE MOUNDS. 171 



flows, while it was prima facie improbable that such a 

 mountain chain as that before us should be altogether 

 formed of the sandstone of which, so far as we could see, 

 the blocks before us were exclusively composed. Soon 

 after leaving Tasseremout, we came to the opening of a 

 narrow valley or ravine cutting through the escarpment, 

 and exposing to view great piles of boulders similar to 

 those seen below, but on a larger scale. After this, the 

 escarpment showed an unbroken face for a distance of 

 about ten miles. Seen near at hand the slope, which 

 from a distance seemed nearly vertical, appeared to have 

 an inclination of from 35° to 45°, and rose to an average 

 height of about 1,000 feet above its base. The upper beds, 

 whose exposed edges were everywhere seen, seemed to 

 consist of hard limestone with siliceous concretions ; while 

 the lower beds were of less consistent shaly limestone. 



The ground over which we rode in a SW. direction, 

 parallel to the base of the escarpment, was very irregular 

 in form, rising in places into mounds sloping inwards 

 towards the cliffs as well as outwards towards the plain ; 

 and, although in great part covered with vegetation, it 

 appeared pretty certain that the whole was composed of 

 irregular masses of sandstone intermixed to some extent 

 with fragments of the rocks forming the barrier beside us. 

 To those who did not admit the probability of the boulders 

 before seen being deposited by glacial action, the phe- 

 nomena here presented offered strong confirmation. A 

 glacier descending from a main valley necessarily flows 

 down the slope towards the plain, and could not turn 

 aside at right angles to its previous course, and to the line 

 of maximum inclination, unless there had been a barrier 

 of solid rock stopping the way, of which there was here 

 not the slightest indication. Whether or not materials 

 that are borne down a steep incline by sub-aerial denu- 

 dation form a talus with a diminishing slope resting 

 against the face of the escarpment, or form mounds at a 

 greater or less distance from the base, is a question de- 



