GEOLOGY OP CENTRAL WASHINGTON TERRITORY. 
477 
masses had fallen from the inferior layers of what remained, showing that the work of destruc¬ 
tion was still going on. The bed of the water-course was about twenty-five feet beneath the 
surface, and the vaults were from twenty-five to thirty feet wide, and fifteen or twenty in height. 
The under side of the strata occasionally exhibited fluxures, resembling waves of progression. 
Small stalactites of infiltration hung from the roof and walls, and stalagmites had been deposited 
on the floor. This remarkable passage was traced at intervals for three or four miles, and 
probably terminates in a branch of the Klikatat river crossed by the party the next day. 
The Indian guide obtained snow from some cavity in this field, and reported that there was 
one hole into which, if a stone was dropped, a long time elapsed before it was heard to strike. 
The soil of the valley which we descended consisted ol a yellowish, light sandy loam, for the 
most part thin, and lying directly upon the basalt. Lower down the mountain it became deeper, 
and on the banks of the streams showed a depth of six or eight feet. Below the limit of the firs 
the forest was open, and the ground covered with an abundant growth of excellent grass, forming 
a good stock-range during the summer season. It is believed that wheat would flourish here; 
but the general want of water, except on the streams, and the coldness of the climate, will probably 
prevent its occupation except for grazing. With this branch of the Klikatat river a further change 
occurs in the rock, the range of hills lying to the east of it consisting of the same gray trap 
noticed in the ascent from the Cathlapoot’l, and, it would seem, bounding the efflux from the 
mountains in this direction. From the cursory observations of this journey, it is inferred that the 
more recent lava from these sources is confined within a particular basin, separated by well- 
defined boundaries from the basalt of the prairies, from which it differs considerably in apparent 
structure, and probably in composition also. Should a thorough geological exploration of this 
region be hereafter undertaken, it will prove a matter of interest to trace up the course of the 
streams, and fix the true relations of the existing volcanic peaks to these formations. 
Between the branches of the Klikatat is the Tahk prairie, the waters of which communicate 
with the main river. It is about six miles in length, by a mile in its greatest width, and is 
1,268 feet above Vancouver. A shallow, marshy lake occupies its lower end, the remains of 
one which formerly covered the whole and extended much beyond the present bounds of the 
open land. It is a favorite kamas and w r appatoo ground of the Indians. The soil is a bluish clay, 
baking very hard and cracking in the sun, and forms a great contrast with that bordering it, which 
is light and pulverulent, and deeply colored by oxide of iron. The dark hornblende rock first 
noticed on the Yakohtl occurred in place again here, but much more impregnated with iron. 
The hills are barren and covered with scattered blocks. The main Klikatat river we found 
running in a bed about two hundred feet below the general surface. It was at this season 
(August 13) thirty or forty yards wide, and up to the flanks of the horses, with a pretty swift cur¬ 
rent. Its advantages for lumbering deserve particular attention. The yellow pine is found in 
abundance, of excellent quality and suitable size, everywhere upon its banks, and logs can be 
run at any season of the year without much difficulty to the Columbia. This river heads in 
Mount Adams. The boulders in its bed resemble in every respect those found in the Cathlapoot’l. 
Its intersection with the trail is the lowest point touched by the main party from the time of 
leaving the Cathlapoot’l to that of reaching the Columbia below the Pisquouse. The descent 
of the Cascade range may be considered as terminating here, and the survey of its eastern slope 
to have commenced. 
The Sahpenis, the first branch of the Yakima encountered upon the route, appears also to head 
in Mount Adams. It is divided from the Klikatat by a range of hills rising to the height of 3,600 
feet, and its bed, though in a very deep canon, is much more elevated than that of the Klikatat. 
The walls of this ravine are basaltic precipices rising in steps. The country here first begins to 
open, exhibiting bald prairies seen at a great height upon the hills, and between it and the Simkwe 
the forest disappears altogether. The fact was noticed by Lieut. Wilkes, in his memoir on West¬ 
ern America, that south of 48th parallel the line of forest terminates at about the same distance 
