222 BERTHA'S VISIT TO HER 



other important consequence of this inclined dis- 

 tribution of the strata, is the variety of minerals 

 which it enables mankind to obtain. If they were 

 all horizontal, one country would be all marble, 

 another all coal ; but by this beautiful irregularity 

 of nature, everything that is useful approaches 

 the surface some where or other, and puts itself 

 within reach of the industry of man." 



" Are all the strata, then, sloped at this useful 

 angle of which you speak ?" 



" Oh no, Bertha," my uncle replied; "they 

 are inclined at every conceivable angle, from 

 perfect horizontality in some places, to a vertical 

 face in others." 



Caroline observed that even the strata at 

 which we were looking did not all appear to 

 have the same dip, and wondered what could 

 be the cause of the difference. My uncle said 

 she was quite right in the fact ; the strata at the 

 eastern end of the valley had evidently a more 

 sudden dip than the rest. " But," he continued, 

 " it is to facts, my little geologists, that we must 

 at first confine ourselves : though causes and 

 theories are highly interesting, at present they 

 would only bewilder you. Those numerous 

 strata, however, will afford some illustration of 

 what I told you a few days ago about forma- 

 tions. You see by the frequent repetitions of the 

 same substances in the cliff, that the same strata 

 are frequently repeated, and in the same order. 



