■GEOLOGY OF THE KLONDIKE GOLD FIELDS. 305 



difficult to gauge by the standard of the iiiei'ciii'i;il index. I shall 

 not hazard a guess as to the actual reading. 



Taking the mountains in their entirety, it is ditHcult from single 

 points of view to determine for them any definite relation. There 

 are so many valleys in close proximity to one another, some very 

 ancient and others relatively modern, and with trends so opposed in 

 all directions, that in the absence of a dominant ridge or mass this 

 relation becomes very confused; and I was not in a position, with 

 the limited time at my command and the deficiency of rock out- 

 crops, to positively define any main line or axis of uplifts. Yet I 

 suspect that there is one such, with a generally east and west bear- 

 ing, whose trend might correspond with that of the ridge already 

 referred to, which, with a southwesterly deflection, unites Dome 

 Mountain with the mass that separates the upper Eldorado from 

 Chief Gulch. What strikes one as particularly interesting in the 

 conformation of some of these mountains when seen from an ele- 

 vation is their hummocky appearance. This is particularly notice- 

 able in the mountains which close in the Eldorado and Bonanza Val- 

 leys. With considerable actual elevations, the}'- convey the impres- 

 sion of being merely swells or undulations of an open surface, very 

 much like magnified morainic knolls in a glaciated country. This 

 depressed type of mountain structure, with the evidence of its ex- 

 panded valleys and gently flowing contours, carries with it the proof 

 of long-continued degradation, and of a history whose pages read 

 far back into geological chronology. 



AVitli the evidences of antiquity before us, there are yet indi- 

 cations, amounting, it seems to me, almost to proof, that many of 

 the more pronounced features of the region date their origin from 

 only a comparatively recent period. Such is the case with a num- 

 ber of valleys that are tributary to the main ones, and even the 

 latter appear to have been modified by late stream displacements. 

 Taking the Eldorado or Bonanza, with their open U-shaped troughs 

 and in most parts gently sloping banks, as types of the older valleys, 

 it is surprising to note how many of their tributaries have the deeply 

 incised and narrow contours; and I am led almost to conclude that 

 some of these are really of very late construction. The stream dis- 

 placements, which, by reason of the indices they give to the finding 

 of new placers, are now beginning to be so attentively studied by 

 the miner and prospector, are emphatic in their testimony in this 

 direction.* One has but to note the triangular area that is included 



* Prof. Israel Rugsell has made the interesting observation that orographic movement 

 may now be taking place in the region of "the middle Yukon, about the Lower Rampaits, 

 with the uplifting of a mountain range athwart the river ; on this supposition he seeks an 

 explanation for the detail of the Yukon lowlands. 



