jj^jj^.j^,^] GEOLOGY STEATIGEAPHY OF THE EAST SLOPE. 145 



sea. The channels of drainage started were directed solely by the struc- 

 ture and characters of the upper rocks, and when they gradually cut 

 down through these and commenced sinking their canons into the under- 

 lying complicated rocks, these canons bore no relation whatever to their 

 complications. It is but recently that the upper rocks have been com- 

 pletely removed from the summits of the mountain-spurs, the ancient 

 level of subaqueous erosion being still indicated by the often uniform 

 level of the spurs and hill-tops over considerable areas, and large plateau- 

 like regions which became very marked from certain points of view. 

 Two or three such levels are indicated at a few places, showing not only 

 that the sedimentaries have once extended up over what are now the 

 mountain rocks, but that the uplifting has* been mainly confined along 

 certain partly well-defined lines, the intermediate belts, though uplifted 

 bodily, remaining comparatively level, a type of folding, probably, not 

 uncommon farther west, and which will be referred to again in the fol- 

 lowing chapter. 



Eroded away, worked farther and farther back, the sedimentaries 

 have- receded to the line of hog-backs, and having a structure bearing a 

 partly constant relation to the eroding forces, with persistent lithologi- 

 cal characters, their topographical features indicate their geological 

 structure, and it is through the former that the latter may be most rapidly 

 and easily read, the long ridges nearly always, as shown in Chapter 11, 

 conforming to a particular bed or series of beds harder than their neigh- 

 bors, and thus traceable as far as the ridge is visible. Not so the meta- 

 morphics. Penetrating the formerly covering sedementaries, the canons 

 commenced sinking into the lower and more complicated rocks, with 

 directions impressed upon them by the latest uplift and the overlying 

 rocks, and bearing no constant relation to the structure of the lower 

 ones in which we now find them. It is true that the structure of the 

 lower rocks has begun to affect the courses of the streams, and in places 

 to a considerable extent. Meeting a softer bed a canon will often have 

 its course directed by it, and follow it for some distance, leaving the 

 adjacent harder beds plainly indicated by the ridges, and sometimes the 

 sinuosities of structure are very curiously followed by a stream in all its 

 windings, but it soon breaks away and runs independently of the bed- 

 ding. Many of the smaller ravines have had their positions determined 

 by the structure; but in a broad sense the drainage is from the main mount- 

 ain crest eastward, independent of structure. Thus, while in places 

 geological features may find expression in surface form, yet, as often, 

 there may be no conceivable relation between topography and geology. 

 The subaqueous erosion, in smoothing all to a common level, destroys 

 all former surface expression of geological character, and the present 

 erosion has not yet been in progress sufficiently long to recreate the 

 lost features. 



With geological structure but feebly featured upon the surfiice, and 

 with such structure as does exist, not only complicated, but often lost 

 in metamorpliism, it becomes no easy task to trace it out, often requiring 

 close inspection of the rock, and^even long search to detect it, while but 

 little definite character can be made out in distant views. On theo_ther 

 hand, the exposures are both numerous and continuous, the many canons 

 aftbrding fine sections of the rocks, and when sufficient time is expended 

 in their examination I conceive that some exceedingly interesting and 

 clear results as to metamorphic action will follow, to say nothing of 

 structural features, and the connection of both with the filling the innu- 

 merable mineral veins which occur in the series with their valuable ores. 

 Kotwithstanding the natnral difficulties in the way, many observations 

 10 G s 



