CHAP. VI. LEDGES ON HILL-SIDES. 281 



bleached petioles, in comparison with those 

 of other plants of the same kind, where 

 there had been no such accumulation. The 

 earth thus accumulated had no doubt been 

 secured (as I have everywhere seen) by the 

 smaller roots of the plants. After describing 

 this and other analogous cases, Dr. King con- 

 cludes : " I can have no doubt that worms 

 " help greatly in the process of denudation." 



Ledges of earth on steep hill-sides. Little 

 horizontal ledges, one above another, have been 

 observed on steep grassy slopes in many parts 

 of the world. Their formation has been 

 attributed to animals travelling repeatedly 

 along the slope in the same horizontal lines 

 while grazing, and that they do thus move and 

 use the ledges is certain ; but Professor Hens- 

 low (a most careful observer) told Sir J. Hooker 

 that he was convinced that this was not the 

 sole cause of their formation. Sir J. Hooker 

 saw such ledges on the Himalayan and Atlas 

 ranges, where there were no domesticated 

 animals and not many wild ones ; but these 

 latter would, it is probable, use the ledges at 

 night while grazing like our domesticated 

 animals. A friend observed for me the ledges 



