172 OPENING OF THE OURIKA VALLEY. cu. vii. 



pending upon the momentum with which they descend ; 

 and this again depends on three elements — the weight of 

 the blocks, the steepness, and the length of the slope. If 

 the greater portion of the materials consist of large blocks 

 launched down a steep and long incline, these will travel 

 to a considerable distance from the base of the cUff, and 

 gradually form a barrier that will stop the course of other 

 similar masses, until these accumulate into considerable 

 mounds, as may be seen in many instances of berg-falls in 

 the Alps. Whatever be the origin of these accumulations 

 in this part of the Great Atlas, it would appear that the 

 conditions that gave rise to them have now ceased, as we 

 saw no instance of any large block that appeared to have 

 been recently borne to its present position. 



As it was important to reach our night quarters by 

 daylight, we collected few plants during the afternoon 

 ride ; a fine Asperula, with numerous flowers varying 

 from white to pink, seemingly not different from the 

 Spanish A. hirsuta, was a great ornament here, and in 

 several other places on the skirts of the Atlas. 



As we approached the opening of a considerable valley, 

 it was apparent that the escarpment ridge here comes to 

 an end, and is not again traceable as a distinct feature in 

 the scenery on the west side of the Ourika river. The 

 name Ourika, with which we now became familiar, appears 

 to be that of a district, governed by a Kaid under the 

 orders of El Grraoui, which includes a fruitful valley run- 

 ning deep into the heart of the Great Atlas. Having 

 descended from the hummocky ground over which our 

 course lay, we struck the valley just where the stream 

 issues from between the hills below a village named 

 Achliz. Nearly all the water was at this season diverted 

 from its natural bed into irrigation channels that are 

 carried through the plain of Marocco. We rode some 

 way along one of these channels, bordered by tall reeds, 

 and a grand Senecio, fully eight feet high, but not yet in 

 flower, probably S. giganteus of Desfontaines. The wide 



