Glacial PhcnoiHcna in ]Vashi)igto)i. — Daiuso/i. 215 
traveled blocks can be found only on the east bank of 
the Columbia or in the region east of the Okanogan river, 
that swept by the eastern flank of the Okanogan glacier. 
A notable aggregation of these boulders is to be seen in the 
Columbia valley a little below the entrance of the Methow. 
The appearance of the great boulder-field there found is diffi- 
cult to account for. Starting on the bottom land only a little 
removed from the high water line of the Columbia river, large 
blocks of rock as big as houses are scattered over forty acres. 
As we ascend the gently sloping hillside going westward, we 
have to pick our way through promiscuously heaped boulders 
of gradually diminishing size. As we traverse the hill for a 
half a mile, we shall find a tolerably constant gradation of 
size until the upper limits of the field are obscured by terrace 
material. Now, throughout this rock scale the proportion of 
basalt to granitic boulders is about one in a hundred. They 
mark, perhaps, a recessional phase, at a time when the Okan- 
ogan glacier was held in check by the now released but swollen 
waters of the Methow^ which forced the glacier to drop its load 
and was yet fierce enough to remove the finer material. Fur- 
ther than that, their present sorted appearance is hard to ex- 
plain. 
But to return to the subject of terraces: w'e notice that in 
the Chelan valley there must have been a time after the par- 
tial recession of the ice, while yet the ice occupied the Co- 
lumbia gorge, when the pent-up waters filled the lower end of 
the valley. This feature is indicated at various levels, but espe- 
cially at the 225 foot level, where the material of lateral mo- 
raines was worked over and spread out in benches, which are 
now capped by a fertile soil. 
One of the late phases in the retreat of the lake waters is 
to be read in the Wapato district. This is a comparatively 
level section of land which occupies the angle of a bend in the 
lake, where it emerges from the north and south Narrows to 
open into the eastward-stretching terminal sheet. At the knee 
of this bend a valley opens westward. Down this valley a 
glacier flowed. Moreover, it did not tarry until its foot rested 
against the angle of the Wapato section, thus forcing the lake 
waters to cross between it and the highland opposite. The 
broad and shallow channel thus formed is now completely 
