122 EEPOKT UNITED STATES GEOLOGICAL SUET'EY. 



considerable deposits of yellow sulphur. A cave-like vent at the lower end of the 

 pool keeps up a constant hissing and roaring. The air in the vicinity is loaded with 

 the peculiar odor of sulphureted hydrogen. 



This part of the valley seems to have been the site of many ancient springs, as the 

 rhyolites which form the lower slopes and the heavy breccias which form the summits 

 of the hills seem to be much altered by solfataric action. 



About half a mile farther down the valley and only a few rods from the creek I came 

 upon another group of hot springs and steam and sulphur (?) vents. The central feat- 

 ure is a broad shallow basin, partly filled with yellowii^h-gray water, which is kept 

 constantly pulsating and bubbling by rising gases which issue from innumerable vents 

 in the bottom of the basin. An area of some 20 yards in diameter surrounding this 

 uncanny pool is covered with hillocks of whitish and reddish clay, from which issue 

 small jets of steam or muddy water. 



On the opposite side of the creek, near the base of the hill which borders the bottom 

 land, is a boiling spring or geyser worthy of note. The pool of slightly turbid water 

 is about 12 feet in diameter. The spring issues from the bank at the north side of the 

 pool. The jets of water, which are driven upward with considerable force, strike a 

 projecting ledge of tufa and are thrown obliquely upward to the height of 10 or 15 feet. 

 The action is almost constant, but the flow of water is exceediugly slight. Descending 

 the creek 2 miles farther, I came out into the open terraced valley of the main stream. 



To the geyser described above by Mr. Holmes I have given the name 

 "West Pelican Geyser." 



PELICAN CEEEK MUD VOLCANO. 



In Lippincott's Magazine for July, 1880, Dr. S. Weir Mitchell describes 

 a mud volcano, which, at first, I thought might be on the West Pelican; 

 but after carefully reading the description, I have concluded that it is the 

 one described to us in 1871 by some of our men, and which was said to 

 be east of us as we traveled up Pelican Creek. Another thing that 

 confirms this view is that the West Pelican Springs are only about 13 

 miles from the lake, and the camp from which Dr. Mitchell started to visit 

 the mud volcano was 18 miles from the lake, and, moreover, he ascended 

 the hills on the east side of the valley and descended on the far side. His 

 description is as follows : 



A gradual rising ground, made up of soft sulphureous and calcareous earth, was 

 crowned by a more abrupt rise some 35 feet high, composed of tough gray clay. This 

 was pierced by a cone of regular form about 30 feet across at top and 5 feet at the 

 bottom. On the west, about one-third of the circumference was wanting from a point 

 6 feet above the lowest level, thus enabling one to be at a distance or to stand close 

 by, and yet see to the bottom of the i)it. The ground all around and the shrubs 

 and trees were dotted thick with flakes of dry mud, which gave, at a distance, a curi- 

 ous stippled look to the mud-spattered surfaces. As I stood watching the volcano, I 

 could see through the clouds of steam it steadily emitted that the bottom was full of 

 dark-gray clay mud, thicker than a good mush, and that, apparently, there were two 

 or more vents. The outbreak of imprisoned steam at intei'vals of a half minute or 

 more threw the mud in small fig-Lke masses from 5 to 40 feet in air with a dull, boom- 

 ing sound, sometimes loud enough to be heard for miles through the awful stillness of 

 these lonely hills. It is clear from the fact of our finding these mud patches at least 

 100 yards from the crater, that at times much more violent explosions take place. The 

 constant plastering of the slopes of the crater which these explosions cause tends to 

 seal up its vent, but the greater explosions cleanse it at times, and all. the while the 

 steam softens the masses on the sides, so that they slip back into the boiling caldron 

 below. As one faces the slit in the cone there lies to the right a pool of creamj^ thin 

 mud, white and yellow, feebly boiling. It is some 30 feet wide, and must be not more 

 than 20 feet from the crater ; its level I guessed at 16 feet above that of the bottom of 

 the crater. 



After an hour's observation near to the volcano, I retired some 50 feet, and, shelter- 

 ing myself under a stunted pine, waited in the hope of seeing a greater outbreak. 

 After an hour more the boiling lessened and the frequent explosions ceased for per- 

 haps fifteen minutes. Then of a sudden came a booming sound, followed by a hoarse 

 noise, as the crater filled with steam, out of which shot, some 75 feet in air, about a 

 cart-load of mud. It fell over an area of 50 yards aroiind the crater in large or small 

 masses, which iiattened as they struck. As soon as it ended I walked towards the 

 crater. A moment later a second squirt shot out sideways and fell in a line athwart 

 the mud-pool near by, crossing the spot where I had been standing so long, and cover- 



