116 



GEOLOGICAL SURVEY OF THE TEEEITORIES. 



of trachyte apparently stratified and inclining 10° to 15° from the val- 

 ley. The vegetation grows remarkably rank along the streams and in 

 the valley where the crust of silica does not prevent it. The perpetual 

 warmth caused by the proximity of the springs is undoubtedly very fa- 

 vorable to the growth of plants. 



We camped the evening of August 5, in the middle of the Tipper 

 Geyser Basin, in the midst of some of the grandest geysers in 



Fig. 



the world. Colonel Barlow and 

 Captain Heap, of the United 

 States Engineers, were camped 

 on the oi)posite side of the 

 Fire-Hole. Soon after reaching 

 camp a tremendous rumbling 

 was heard, shaking the ground 

 in every direction, and, soon 

 a column of steam burst forth 

 from a crater , near the edge of 

 the east side of the river. Fol- 

 lowing the steam, arose, by a 

 succession of impulses, a col- 

 umn of water, apparently 6 feet 

 in diameter, to the height of 200 

 feet, while the steam ascended 

 a thousand feet or more. It 

 would be difficult to describe the 

 intense excitement which atten- 

 ded smeh a display. It is prob- 

 able that if we could have re- 

 mained in the valley several 

 days, and become accustomed to 

 all the preliminary warnings, the 

 excitement would have ceasecl, 

 and we could have admired 

 calmly the marvelous ease and 

 beauty with which this column 

 of hot water was held up to that 

 great height for the space of 

 twenty minutes. After the dis- 

 play is over the water settles 

 down in the basin several inches 

 and the temioerature slowly faUs 

 to 150°. We called this the 

 Grand Geyser, for its power 

 seemed greater than any other 

 of which we obtained any knowl- 

 edge in the valley. (Fig, 47.) 

 There are two orifices in one ba- 

 sin ; one of them seems to have no raised rim, and is a very modest-looking 

 spring in a state of quiescence, and no one would for a moment suspect 

 the power that was temporarily slumbering below. The orifice is oblong, 

 2^ by 4 feet, while for the space of 10 feet in every direction around it 

 are rounded masses of silica, from a few inches to 3 feet in diameter, 

 looking like spongiform corals. Nothing could exceed the crystal clear- 

 ness of the water. This is the Grand Geyser. Within 20 feet of this 

 orifice is a second one, of irregular quadrangular form, 15 by 25 feet ; 

 the east side of the main outer rim of reservoir extended 20 feet beyond 



GRAND GEYSER. 



