BLACK HILLS GEOLOGY. 



195 



the Sharp Crest of Terry's Peak. It then falls as gradually to 

 the north, the various hill-tops seeming to arrange themselves 

 one after another in the order of their elevation so as to scarcely 

 interrupt the even contour of the declining country. (See 

 Figure 6.) 



III. STRATIGRAPHY. 



It is not the purpose of this paper to enter into an extended 

 discussion of the stratigraphy, but in order that the geological 

 relations of the eruptive rocks and of the ore-bodies may be 

 clearly understood, a brief exposition of the separate formations 



CAMBRIAN SHALES 



ALGOHKIAN SLATES, OUARniTES ETC. 



Fig. 7. Generalized section of the sedimentary rocks. Taken mainly from ex- 

 posures near Elmore on the Burlington and Missouri River R. R. 



