RELATIVE AMOUNT OP MATERIAL LOST 273 



of running water, these figures, though suggestive and instruetive, 

 fall far short of showing the full extent of the decay. 



(10) Eelative Amount of Material Lost. — Other things being 

 equal, it is also safe to infer that more material has actually 

 been lost through disintegration and decomposition in moun- 

 tainous and hilly countries than from the level plains. This 

 for the reasons that (1) through the upturning of the beds there 

 were exposed, it may be, friable and soluble strata that might 

 otherwise have been protected, and (2) that through the shat- 

 tering incident to this upturning the rocks were rendered more 

 susceptible to the weathering forces.^ Further, (3) the steeper 

 slopes in mountain regions promote more rapid removal of the 

 resultant debris, whereby fresh surfaces are continually exposed, 

 such as might otherwise shortly become protected through its 

 accumulation, as above noted. 



^According to Van Hise (Treatise on Metamorphisin) minerals in a 

 condition of strain as commonly existing in compressed, folded and sheared 

 roeks, are more readily acted upon by underground solutions than when in 

 their normal condition. 



19 



