GEOLOGICAL SUEVEY OF THE TEEEITOEIES. 245 



extends up the stream on both sides about a half mile. In the upper 

 edge of the narrow belt of timber which separates the spring-area from 

 the lake-shore, is a small mud-pot, whose borders were ornamented 

 with exquisite cock'scomb-like deposits of a bluish-gray geyserite, con- 

 taining sufficient clay to give their pointed tips far more toughness 

 than their form would lead one to expect. These forms have not been 

 seen at any other point. 



About tifty yards west from this point stands the most important 

 geyser of the basin. It has now three vents, standing closely in a row, 

 each of which has built up a small mound, beautifully beaded without 

 and pointed within. The eastern vent has an irregularly-oblong open- 

 ing, about 2 feet long and from 8 to 12 inches wide; its mound is 

 about a foot high, and stands upon a base of about 3 feet by 4. The 

 central mound is about 5 feet in diameter at the base, and about 3 feet 

 high, with a deep central, triangular opening, measuring about 30 inches 

 on a side. The western one is about 1 foot high, on a base of about 

 20 by 30 inches, with two small openings about 2 or 3 inches in diame- 

 ter. These stand in the mouth of an old geyser, once probably of great 

 power, though now nearly inactive, of which there remains a deep pool 

 about 8 feet wide by 12 feet long, in which the surface of the water 

 during our stay at this camp was about 3 feet below the top ; but it 

 evidentlj' overflows at times, and it is possible that it still spouts 

 occasionally. It showed no sympathy' with tfie present vents during 

 their eruptions. The section of the layers couvstituting the old mound 

 is well shown in the walls of this pit. During eruptions, the west vent 

 spouts a little water, 2 or 3 feet higli, for from 1 to 2 minutes, and then 

 yields a moderate flow of steam. Meanwhile, the center vent is throw- 

 ing a very powerful jet from 70 to 90 feet into the air, which, after about 

 5 minutes, gradually gives place to steam, the mingled steam and water 

 giving the highest jets. The east vent, spouting from 10 to 50 feet, 

 throws a solid" body of water for about 10 minutes, when the whole 

 supply of water seems to be exhausted, and the rush of steam from all 

 the vents becomes more violent and continues some 10 to 50 minutes 

 longer, gradually declining, however, though with many spasmodic 

 renewals. A small flat opening in the space between the central and 

 western vents gives exit to a little water while the geyser is preparing 

 for eruption, but takes no part in the eruption itself. We called this 

 Union Geyser, because of its combination of the various forms of gey- 

 seric action. Its temperature, immediately before eruption, was 198'^. 

 Its periods of eruption are irregular, and no law of irregularity was 

 ascertained. An eruption was heard by the men on guard on the night 

 after our arrival, but the time was not noted. The hrst recorded one 

 began at 10.28 a. m., and continued, steam and all, 47 minutes. Its 

 highest jet reached the elevation of 92 feet. The next began at 1.53 

 ]). m. on the same day, reached 70 feet in height, and lasted 50 minutes. 

 Still another was heard at 10.25 p. m., but no further time observations 

 were recorded. 



About this spot, there are several quiet and boiling springs ; but 

 none of the latter spout more than from 1 to 3 feet. Passing up this 

 side of the stream, however, for about a hundred yards, we find, just 

 above the point of the hill upon our right, the first of a group of larger 

 vents, of which several seemed to us to deserve names. This, which 

 was called the Minute ]\Ian, has built up a mound about 4 feet high and 

 from 12 to 15 feet across, beautifully ornamented with bead- work and 

 with the sliarp points which usually accompany the uion.' frequent and 

 abundant flows of water. This ornamental wurk spreads far beyond 



