214 TJic American Geologist. October, i898 
"a broad terrace 325 feet above the lake" in the Chelan valley 
with the "great terrace" of the Columbia valley, and for this 
purpose invokes the aid of a great post-glacial "lake Lewis," 
which should have formed the two terraces at the same time. 
The Chelan terrace, by the way, is more nearly 225 feet above 
the lake, and even so, some 250 feet above the top of the Co- 
lumbia terrace. 
We shall return in a moment to speak of the conditions at 
the foot of lake Chelan, but first a word further as to the 
Columbia terrace. That it is a river and not a lake forma- 
tion would seem to be sufficiently evidenced by the fact that 
the terrace maintains its relative hight above the rivers — Co- 
lumbia and Okanogan — throughout a distance of at least forty 
miles. Thus the absolute hight of the terrace increases as we 
ascend the streams. Furthermore, the material of the terraces 
shows nothing of the offshore gradation which we should ex- 
pect in a still water deposit. This point cannot, of course, be 
urged if one insists with Russell that the whole channel was 
filled by lake-formed terrace deposits; but this is manifestly 
improbable. 
The Chelan glacier, when it encountered the Columbia 
river, began to deposit a moraine across the mouth of its val- 
ley. This deposition was kept up at least until the Columbia 
valley was occupied by the southward flowing, west fork of 
the Okanogan glacier. As the ice began to retreat, it is pos- 
sible to suppose that both the Chelan and Methow glaciers 
began to withdraw at first, while the Okanogan glacier still 
filled the Columbia gorge, and that the ice of the latter bulged 
into and followed the path of the retiring glaciers. This ap- 
parently out-of-the-way explanation is called for because of 
the remarkable presence of certain boulders in the Chelan and 
Methow valleys. Distributed all along the western bank of 
the Columbia river, and at certain points in the lower Methow 
and Chelan valleys, there occur large rounded masses of 
basalt, boulders, brought by the ice. I saw two on the 
Methow at least five miles from the mouth of the river. 
Another near lake Chelan weighing hundreds of tons 
lies half buried in the hillside about fifty feet above 
water on the north shore of the lake, and also five miles 
from the Columbia. The possible parent beds of these 
