2I( 
The American Geolosist. 
October, I89S 
evacuated by the lake waters, and is occupied through its five 
or six miles extent only by occasional alkali sinks. 
Lake Chelan is held in place by a dam of glacial debris. 
The terminal moraine of the Chelan glacier chokes up the 
lower valley and holds the lake back at a level 325 feet above 
that (3f the Columbia river, which sweeps its base. Instead of 
Diagram Ivo. 4. 
excavating a channel through the heaped-up materials of the 
moraine and so reducing the lake to its preglacial level, the 
outlet of lake Chelan has found another route,— a precipitous 
channel through the granite. This course is, perhaps, deter- 
mined, as Mr. Russell suggests, by the fracture-line between 
two immense fallen rock masses, which were at some time split 
ofif from the north-east corner of Chelan butte. At the time of 
the Kokshut mountain disaster water coming from some point 
in the river burst forth from under the moraine, and has since 
persisted as a series of springs, — making a veritable garden 
spot at La Chapelle's landing, where was only barren sand be- 
fore. If it be true that the Chelan river, instead of cutting 
through the granite, has merely followed a break in the rock, 
then no reliable estimate of its age can be formed on this basis. 
(See diagram No. 4.) Better results, however, may be ex- 
