GEOLOGY OF CENTRAL WASHINGTON TERRITORY. 475 



covered the ground for some hundred yards beyond it, and pumice was occasionally found along 

 the route. This is supposed to be the most recent lava ejected from St. Helens. 



Leaving the Cathlapoot l, we commenced the ascent of the Cascade range. The eastern side 

 of the valley rises in high tables, with level tops and steep banks, which are continued to the 

 summit. Unfortunately, we could obtain no view of the country, the smoke from the burning 

 timber, which had prevailed for some days, effectually obscuring the atmosphere. The rock in 

 place was a gray feldspathic trap, covered on the surface with a whitish coating. Large, loose 

 blocks of the same and of trachyte were scattered around. Basalt prevails upon the summit, 

 and forms turrets and pinnacles on some of the heights around St. Helens and Mount Adams. 

 Elsewhere the hills are covered with reddish scoria. One field of lava was passed, fractured in 

 the same manner as that on the Cathlapoot l, but apparently of older date, and assuming columnar 

 forms, which was not the case with the latter. 



The height of Chequoss where the party encamped from the 8th to the 10th of August was 

 4,053 feet. It is a circular basin, containing a small pond, one of ,a number lying at the head of 

 the White Salmon river, and presenting the appearance of an ancient crater. Notwithstanding 

 its elevation, this spot is tolerably fertile ; the basin, as well as the hills around it, being covered 

 with grass and producing strawberries in profusion, which were in season at the time of our visit. 

 The soil of the mountains is a yellowish loam, except where colored by the decomposition of 

 scoria. The character of the forest changes entirely with the summit of the Cascades. The 

 details of this change belong to another report, but it is proper to refer to it in connexion with the 

 geological face of the country. The arbor vitas does not cross the dividing ridge; the firs and 

 spruces are speedily lost, and succeeded at first by intermixed larches and pines, and lower 

 down by the pine alone. The larch seems to be confined altogether to the eastern side of the 

 mountains, and the long-leaved pines nearly so. The limit of the firs on the eastern slope would 

 seem to be not far from three thousand feet above the Columbia. The forest retains a consid 

 erable size to nearly four thousand feet. 



During our stay at Chequoss the weather was only at intervals clear enough to afford a view 

 of the mountains ; with the exception of the great snow-peaks, their aspect is that of a chaos of 

 hills, of very equal height, rising from an elevated plateau, but few points rising to a greater eleva 

 tion than 5,000 feet, which is about that of the snow-line on Mount Adams. No ranges of any 

 great length were distinguish able ; the sides of the hills were long, sweeping slopes, enclosing shal 

 low valleys which extend to the very feet of Mounts St. Helens and Adams, and some of which 

 contain marshy prairies, the beds of ponds. The range in this part appears to be about thirty 

 miles in width at the base and fifteen on the top, the steepest slope being to the west. From the 

 hills around Chequoss, the five snow-peaks Mounts Hood, Jefferson, St. Helens, Adams, and 

 Rainier were visible, Mounts Hood and Jefferson bearing southwesterly ; Mount St. Helens 

 nearly northwest ; Mount Rainier a little west of north, and Mount Adams north. The latter was 

 riot more than fifteen or twenty miles distant. The height of Mount Rainier, as given by Cap 

 tain Wilkes, is 12,330 feet, and that of St. Helens 9,550 ; from which last Mount Adams does 

 not apparently vary much. It is not a little singular that neither Lewis and Clark, nor Lieut. 

 Wilkes, distinguished Mount Adams as a separate peak from St. Helens ; for, although they 

 resemble each other considerably in general form, their positions and range are very different. 

 Mount Adams alone is visible from the Dalles ; but both of them, as well as Rainier, can be 

 seen from a slight elevation at the mouth of the Willamette. The sketches of Lieut. Duncan, 

 accompanying the reports, will better convey an idea of these mountains than a mere verbal 

 description. The angle of incidence of their sides was taken by a clinometer. The steepest 

 continuous face of St. Helens, disregarding precipices, was about 40, and none of the others 

 exhibit a greater declivity. The crater of Mount Hood is on its south side ; that of Mount St. 

 Helens on the northwest, and of Mount Adams apparently on the east; that of Rainier seems to 

 have been at the summit. Smoke was distinctly seen issuing from St. Helens during our journey. 



