EFFECT OF DRIVING RAIN, 47 



separated from the terrace of which they formed part, by 

 the action of rain alone. 



A similar phenomenon on a larger scale may be 

 seen among the Wasatch Mountains of the Western States 

 of America, where pinnacles, some of them four hundred 



Fig. 12. BLOCK OF PLUM-PUDDING STONE. 



eet high, fringe the bank of the South river for miles. The 

 plum-pudding stone (Fig. 12) of which they are composed 

 (rounded pebbles cemented together by clay and sandstone) 

 is liable to crack in dry weather, and the rain, eating its 

 way down through these cracks, wears long grooves in the 

 softer stone which it meets with below. A cap of harder 

 stone usually remains for a while on the top of the pinnacle, 

 and protects it from the weather, but when this is blown or 

 worn away the whole monument crumbles down by degrees. 

 A thickness of four hundred feet, and some square miles in 

 extent, of solid rock is entirely gone, with the exception of 

 these pinnacles ; but though worn down by the effect of 

 rain and weather, it has been removed by running water. 



