Glacial Plicnomena hi WasJiingtoii. — Daivson. 207 
Three such glaciers swept down the Chelan, Alethow, and 
Okanogan valleys, respectively. Of these we may well be- 
lieve that the Chelan glacier, both on account of the narrow- 
ness of its valley and the hight of its mountains, was the first 
to reach the Columbia river. In doing so, it forced out the 
waters of the pre-glacial lake Chelan, which must have existed 
at a level some 400 feet below the present one, as a lateral 
reservoir of the Columbia river. Upon reaching the Colum- 
bia, instead of at once and effectually damming up the stream. 
in the struggle which ensued the glacier was held in check 
and its foot dissolved by the impetuous river. Besides this 
it had lateral means of discharge through Knapp's and Na- 
varre's coulees; — hereafter to be more particularly described. 
These lateral ice-streams also emerged upon the Columbia 
river, but at a lower point, where the valley is wider; and to- 
day great benches and banks of morainic and half-sorted ma- 
terial may be found distributed for several miles on the Doug- 
las county side of the river. 
The Methow glacier reached the Cokmibia some time 
later, encountering it at a point which may be called the little 
bend. For here the river, after pursuing a general westerly 
course for upwards of 80 miles, turns sharply within the space 
of half a mile to begin its southern course. At this exact 
point the Methow valley opens to the west. And here is pre- 
served a most interesting record of the time when the ice 
from the west began to encroach upon the river channel. 
Upon becoming dammed the river rose to a hight sufficient 
to enable it to cut across the corner, where it excavated a 
deep transverse channel some 150 feet down into the granite, — 
as shown by accompanying diagram (No. i). The glacier, 
being relieved laterally, left the river in undisturbed posses- 
sion until the final damming of its waters by the Okanogan 
glacier. 
It is by this latter glacier that the hardest work was done. 
Being produced by a drainage area 200 miles long and 6000 
miles in extent, it was slow in coming, but when it did arrive 
it was not to be stopped by the Columbia gorge. It occupied 
this latter completely, dividing right and left, but even so it 
could not find relief for its great bulk and enormous pressure. 
According to Russell it rose and overtopped the plateau op- 
