BOUNDARY WALL OF CRATER. 67 



sometimes applied to the whole mountain mass 

 forming the eastern end of the Teng'ger. In 

 order to descend with our horses into the Sandy 

 sea, we turned to the left and rode along the sum- 

 mit of the ridge, traversing sometimes almost knife- 

 edged crests, merely wide enough for the horse 

 to tread ; coasting sometimes round projecting but- 

 tresses with dizzy corners, on a ledge that seemed 

 to overhang the precipice, or climbing up and 

 slipping down sharp ascents and descents where 

 the wall was broken by a gap, or rose into a 

 higher peak than usual. Still we saw no rock, not 

 even a fragment of stone ; the sharpest ridge, the 

 steepest bank, the very face of the precipice itself, 

 where it was visible, seemed all soil or loam, turning 

 in the beaten path to a slippery clay. This seemed 

 the strangest circumstance to me, and attracted my 

 attention even from the magnificent scenery around. 

 I could not understand why it had not been all worn 

 down or washed away by the rain long ago. No 

 doubt great degradation has taken place, but this is 

 chiefly on the sides of the mountain, as shewn by the 

 multitude of ravines, with their narrow dividing 

 ridges. The very narrowness of the present crests 

 of these ridges, and the steepness of their sides, 

 joined to the clayey nature of the soil, shoots off all 

 the rain into the existing gullies, and any great 

 destruction can only take place now, when these are 

 worn so deep and so far back as to undermine the 

 wall that separates them from each other, or from 



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