3 o8 POPULAR SCIENCE MONTHLY. 



feet presentation of high-level terraces can be had than that which 

 defines the first line of heights, of perhaps one hundred and fifty 

 to two hundred feet, which so beautifully impress the landscape of 

 the Yukon about Dawson. The observer, from a still loftier ele- 

 vation, notes these flat-topped banks, having the regularity of rail- 

 road constructions, following the course of the river as far as the 

 eye can reach, here perhaps interrupted by a too steeply washed 

 buttress, elsewhere washed to low level by some stream which has 

 taken a transverse direction. A somewhat higher line of benches 

 curves around the still higher points of eminence, and defines the 

 course of water across country such, at least, it is to-day. And all 

 the way to the top, scattered evidences of the recent presence of 

 water can still be found. I met with rolled or water-worn pebbles 

 so near to the top (the actual summit and not the position of the 

 signal flag) of the high peak overlooking Dawson that it may safely 

 be assumed that they also occur on the very apex (about eleven hun- 

 dred feet above the present level of the Yukon), a conclusion which 

 is more than strengthened by the finding of pebbles at even a greater 

 elevation on the French-Adams Creek knob. While thus present- 

 ing the evidence of high water levels, I am far from convinced that 

 this evidence points exclusively to river flows. Much more does it 

 appear that, in one part of its history at least, we are dealing with 

 the evidences of the past existence of large lakelike bodies of water, 

 perhaps even of a vast inland sea. The contours of the country in 

 a sort of ill-defined way suggest this interpretation an interpreta- 

 tion that is not, however, without evidence to support it, and which 

 seems also to have been entertained before me by McConnell and 

 by Israel Russell. The latter investigator has, indeed, given the 

 name of Lake Yukon to a former extensive body of water, of which 

 the existing Lakes Lebarge, Marsh, Tagish, and Bennett, with the 

 connecting Yukon, are only dissociated parts. This lake is assumed 

 to have been about one hundred and fifty miles in length, with a 

 surface elevated between twenty-five hundred and twenty-seven 

 hundred feet above the sea. 



First in the line of evidence may perhaps be taken the univer- 

 sality of wash gravel and of terrace debris and the great heights 

 which they occupy. "While I have not myself observed such evi- 

 dences of water action on the very summit of the Dome, there is rea- 

 son to believe that they do or at least did exist. Most of this sum- 

 mit, in its narrowed form and rapidly descending slopes, has been, 

 if one may use the expression, more than washed off, and could 

 hardly be expected to retain for any great length of time accumu- 

 lations of loose fragmental material. But at least its far-off con- 

 tinuation near the source (right fork) of Eldorado Creek bears some 



