3o8 POPULAR SCIENCE MONTHLY. 



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

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

 to two Imndred feet, wliicli so beantifiilly impress tlie landscape of 

 the Yukon about Dawson. 'J'he observer, from a still loftier ele- 

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

 road constructi(Uis, following the coiii'sc 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 dii-cction. 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 nn^t 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 vei-y apex (about eleven hun- 

 di-ed 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-deHned 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 1»y 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 existiiia- l>:ikes Leljaruc, .Marsh, 'I'agish, and Bennett, with the 

 connecting Yukon, are oidy dissociated ])arts. This lake is assumed 

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

 surface (devateil lietweeii twenty-five linndreil and twenty-seven 

 hundred feet above the sea. 



First in the line of evidence may ]ierhaps be taken the univer- 

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

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

 <leiu'es of water action on t lie very sunnnit of the Dome, there is rea- 

 son ti) IxdicAc tliat tliey do or at least did exist. ]\rost of this sum- 

 mit, in its narrowed form and ra])idly descending slojies, has been, 

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

 hardly be exjx'cted to retain foi' any gi-eat length of time accumu- 

 latiojis of loose fragnu'ntal material. Ihit at least its far-off con- 

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



