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side. This is occasioned in the following manner: 

 When the current is propelled into the pot-like hole, 

 the pebbles which are already within it, are driven 

 with considerable force against the up-stream side. If 

 they occasionally fail into the current, w hen it strikes 

 against the lower or down- stream side, they are forci- 

 bly thrown back again, and thus kept playing against 

 the upper side, by which means the hole becomes 

 shelving under. Lastly, the sand and pebbles that 

 are occasionally driven out. produce, by abrasion upon 

 the down- stream side, an ewer-like process or gutter, 

 which is very perceptible in many of them. 



6th. If there are any appearances of a part or por- 

 tion of the side of a mountain having slidden down to 

 its base, what appears to have been the most probable 

 cause of its removal ? and what its original height 

 above the mountain's base ? And moreover, is there 

 any narrow 7 , but extensive valley or channel through 

 subordinate hills, and through which a current may 

 have run, directed against a point where such portion 

 of earth, or rocks, have slidden off? If so, what is its 

 breadth, extent, and direction, in relation to the ridge, 

 or range of the mountain ? 



7th. Are there any rallies, or gaps, that intersect a 

 range of mountains, either strait or circuitous? and 

 what is the greatest probable height of the highest 

 point in such ralley or gap, above the mountain's base ? 



8th. Are there any appearances of the operations of 

 currents in such rallies, either in the earth or upon the 

 rocks that may be exposed ; and above the height at 



