216 TOPOGRAPHICAL REPORT ON WESTERN DIVISION. 
of it have a light gravelly soil; good grass grows upon it. The old Presbyterian mission was 
situated at the lower end of this valley. The valley varies from one to two miles in width, and 
is skirted by low ranges of hills well covered with pine. From the mission the trail runs over a 
low hilly country, covered with open pine woods, to the Spokane river, leaving the Chemakane on 
the right. The descent to and ascent from the Spokane river is abrupt and rocky. There is a 
tolerably good diagonal ford at this point—bottom gravelly and somewhat stony. This river is 
about seventy-five feet wide and three deep, current rapid. A very precipitous, high, rocky bluff 
is on the left bank, half a mile below the ford. All the country between the Slawntehus and 
Chemakane, westward towards the Columbia river, is more or less mountainous or broken by 
irregular ranges. ‘These mountains are higher towards the north, and break up and fall off 
towards the south into low ranges and undulating plains in the great Spokane plateau. The trail 
bears to the southwest from the Spokane river across this plateau—crossing the Saptin or Lewis . 
fork of the Columbia at the mouth of the Peluse. This distance is seventy-six miles. There 
is no timber on this plain, except a few narrow strips of pine wood, which stretch out to the west- 
ward from the Coeur d’Alene mountains on the east. These strips proceed to the westward no 
farther than the trail, and are confined to the country twenty-two miles from the Spokane river. 
A little willow and cotton-wood are also found on the immediate banks of the streams, but in 
small patches. A district of country about twenty-four miles wide commences twelve miles 
south of the Spokane river, and runs east and west nearly, which is the highest portion of the 
Spokane plateau. This district is basaltic and broken, and is covered with innumerable small 
lakes scattered over its surface. These lakes appear to occupy the craters of extinct volcanoes, 
and are fissures formed by the bursting of lava bubbles on cooling. The water in them is fresh, 
and supplies the Peluse and its branches. These lakes are of all sizes; Silkatkwu is the largest 
in the vicinity of the trail. It is five miles long, and varies from one-half to a mile in width. It is 
drained by the Stkahp, a branch of the Peluse. The main Peluse also rises in this region of 
lakes, to the east of the trail. I have no actual observations of the extent of this lake country 
to the east and west, but presume that to the westward, particularly, it must run for many miles; 
at least, up to what is known as the ‘Grande Coulée,” and, perhaps, over to even the great 
western bend of the Columbia itself. The Spokane plateau embraces all the country included 
within the limits of the Coeur d’Alene mountains, the Saptin, Columbia, and Spokane rivers. 
It has an undulating stratum of basalt, which is covered with deposits of earth, sand, and 
gravel. ‘The basalt occasionally crops out, particularly on the lake region and along the streams} 
and large irregular masses, pillars, and‘architectural shapes are scattered over this region. The 
country in such places is rough and broken, and covered with large and small fragments of sharp 
fractured lava. The earth, sand, and gravel form rounded undulating chains, or isolated 
hills or buttes, covered with wild sage and grass, the grass being found on the least sandy 
portions. The plateau generally is high and rolling, and destitute of timber. The soil 
is light and unfit for cultivation. Small tracts of arable land are found near the larger 
lakes and the heads of the streams, but they do not exceed one or two acres: in extent. 
The Cherahna runs in a basaltic dalle or trough for most of its length; the last part of it, before 
its junction with the Peluse, being in a cation of columnar basalt. The Peluse, from the point 
at which we crossed it, runs in a similar deep canon. 'The walls of the trough of the Cherahna 
are not more than twenty feet high. A few stunted willow bushes grow in these canons on the 
immediate banks of the streams. The basaltic walls and hills along the Peluse increase in 
altitude towards the Saptin. The Saptin, at the crossing, is about one hundred and fifty yards 
wide, very deep, rough and rapid. This river, at this point, has no valley, high hills running on 
either side of it. The Peluse is first crossed quarter of a mile below the mouth of the Cherahnas 
and the trail then passes over the hills, leaving the river some distance on the right, and comes 
down to it again three and a half miles from its mouth. Between the trail and the river, on 
the right, the country is much broken and very rough, with a good deal of lava on the surface. 
