286 rHOCEEDINGS OF f^ECTIOX C. 



western g-eologists. In the great region between Hudson Bay and the 

 St. Lawrence Valley the older Huronian rocks are often conformable 

 to the Laurentian and pass gradually into them. The Huronian is the 

 great metalliferous series of eastern Canada and the adjoining States 

 generally, and it has already been found to be more or less auiiferous 

 in nearly all parts of its distribution; whereas gold has been found, 

 and only in traces, in but a few instances in the Upper and not at 

 all in the Lower Laui'entian. ■ The Klondike rocks are certainly very 

 ancient; the series belongs to the Huronian type, and it is not more 

 auriferous here than the rocks of this system are in some localities 

 in the east. 



Geographical and Physical Conditions. 



The Yukon River has a course of about 1,500 miles, from its 

 source, a short distance inland from the Pacific Ocean at Lynn Canal, 

 to its mouth in Norton Sound. The upper or Canadian portion inins 

 north-west, in a narrow valley thi'ough a mountainous country, but soon 

 after it passes into Alaska, it is joined by a large branch from the 

 east side called the Porcupine River; the valley broadens and the 

 direction of the main stream changes suddenly from north-west to 

 west-south-we«t, Avhich is a continuation of the course of the Porcu- 

 pine. Notwithstanding that the upper poition of the Yukon is closely 

 flanked by mountains on both sides all along its course, it maintains an 

 even gfrade throuofhout of about 3 ft. in the mile. In the season of low 

 water it is only deep enough for flat-bottomed steamers, and flows at 

 a nearly imiform rate of 3 or 4 miles an hour over a bottom composed 

 of shingle, gravel, and sand. It is a clear-water stream, and has a 

 width of about 200 yds. at White Horse and 400 at Dawson. 



The Klondike gold district pai-takes of the mountainous character 

 of tlie rest of the Yukon region. Its highest point, called The Dome, 

 is a little north of the centre, and nearly all tlie ridges and valleys 

 radiate from it. Its altitude is 4,250 ft. above the sea, or 3,050 

 above the Yukon River at the town of Dawson, which is 1,200 ft. 

 over sea level. The district has been sun^eyed by the Geological 

 Department, and the contour lines of the hills liave l^een defined at 

 50 ft. intei-vals up to 2,000 ft. 



The map representing this work shows in a striking manner how 

 deeply the district has been dissected into a great number of ridges 

 and hills by the small streams called '' creeks," most of which, like the 

 intervening ridges, radiate from The Dome. The average elevation 

 of the ridges above the valley bottoms is about 1,500 ft. The crests 

 of the ridges are unbroken, so that starting from The Dome and using 

 the proper ridge for the purpose, one may reach any part of the district 

 without crossing a valley. Although the flanks of the ridges are steep, 

 their crests are rounded, with a little bare rock cropping out upon them 

 in some places. Each deep valley starts from a cirque-like depression 

 excavated in the side of a ridge, and it maintains for some distance 

 down the character of a steep-sided ravine, but gradually expands, till, 

 in its lower reaches, it becomes flat-bottomed, although not veiy wide, 

 while the sides liave become more or less distinctly terraced up to a 

 height of 700 ft. above the valley bottoms. 



At the beginning of the Pliocene epoch the whole Yukon region 

 inside of Canadian territory, including the Klondike district, appears 



