GEOGRAPHICAL MEMOIR. 255 
expense. Among the various tributaries of the Walla-Walla are Mill creek, Dry Fork, and the 
Touchet ; and of the Snake river, the Tukanon and the Alpahwah. 
The narrative of this exploration will render it unnecessary to go into minute details descrip- 
tive of these several streams, the object of this memoir being to present the general features, 
and deportment, and spirit of the country. It should, however, be mentioned, in connexion 
with the lake system of this great plain, that in the wooded region north of the Spokane are 
some remarkably picturesque lakes, as Lake Pend d' Oreille, on Clark's Fork, and Lake Rootham, 
some thirty miles northward of Clark's Fork, both of which are graphically described in the 
Oregon Missions of De Smet. . 
Coming now to the country lying between the main Columbia and the Cascade mountains, it 
may be necessary to describe, with some little particularity, the various streams and their several 
tributaries flowing into the main Columbia. A glance at the map shows that the general course 
of these streams is very much to the south, and between them are generally to be found high 
mountain spurs which run to the Columbia itself, overhanging it many hundred feet. "The 
most considerable rivers are the Yakima, with its Pisko, its Atahnam, its Nachess, its Wenass, 
and other tributaries. "The Pisquouse or Wenatshapam river, Lake Chelan and the Chelan river, 
the Methow river and the Okinakane river, which may be described as follows : The Yakima 
rises in the vicinity of the passes of the Cascade range, latitude 47° 15’, from several large and 
beautiful lakes, and, taking a general course to the southeast, runs for 160 miles to its confluence 
with the Columbia, in latitude 48905/. For twenty-five miles down the stream its valley is only 
from half a mile to a mile wide; it then widens out in Ketelas plain, which is ten or fifteen 
miles wide, the river there being ninety feet wide and about three in depth, but very rapid. 
Below this plain the river curves gradually to the south until it receives the waters of the Pisko, 
then turns again eastward to its mouth. Between the Ketelas and Atahnam, for thirty miles, 
the hills again encroach on the val!cy, but below that it again widens out to six or ten miles, 
with numerous branchings among the hills. On the west side, opposite Ketelas plain, three 
streams, the Pteh-num, Emptenum, and Wenass, rise among the hills separating the main 
Yakima from its principal branch, the N achess. These streams are from 15 to 20 miles long, 
and run through small and fertile valleys. Тһе Nachess rises in the vicinity of the Nachess 
Pass, and, running nearly parallel to the Yakima at a distance of fifteen or twenty miles, joins 
it after flowing about fifty miles. It has a valley from half a mile to four miles іп width. The 
Atahnam rises about thirty miles south of it, and runs in a more easterly course, emptying 
about ten miles below ; its valley is smaller than that of the Nachess, but fertile. The Pisko 
rises among the hills east of Mount Adams, and in size and character resembles the Atahnam. 
Only two small branches join the Yakima from the north and east, one running through the 
middle of Ketelas plain from the hills northward, the other running almost directly contrary to 
the upper Yakima from the hills east of its southerly bend. Тһе Pisquouse and Enteatkwu, 
which enter the Columbia near ‘latitude 47° 30’, are, at their mouths, rapid streams, with high 
falls as they descend from the hills at the foot of the Cascade range into the deep valley of the 
Columbia. They are supposed to head in the mountains about thirty miles northwest of it. 
The Chelan rises in a lake which is reported by the Indians to run for thirty miles back among 
the mountains, and approaches to within two miles of the Columbia, into which its outlet falls, 
by a series of cascades, 350 feet in this short distance, in about latitude 47° 45’. 
The Methow rises by several sources in the mountains northwest of Fort Okinakane, and 
