PEALE.J 



UPPER GEYSEE BASIN GEOTTO GEOUP. 



ISTo. 2, Grotto Geyser (Plates XIV andXIVa). — This interestm^ geyser 

 received its name in 1870 from the peculiar shape of the main ©r larger 

 crater, which is hollowed into fantastic arches, beneath which are- grotto- 

 like cavities that act as lateral orifices for the escape of water during am 

 eruption. This crater, which we will call Cone No. 1, is very irr^-gulary 

 and is 8 feet high. The orifice is 2 by 6 feet and 19 feet in depth. On; 

 the north side of the orifice there rises a curious pillar like mass of 

 geyserite. It is somewhat club-shaped, and is about 6 feet in height. 



Cone No. 2 is 19 feet in diameter at the base and 14 feet on top. Ife 

 is 4 feet in height, and has a quadrangular orifice measuring 3 by 5- feet^ 

 in which the water during quiescence is from 10 to 15 feet beloiw the 

 top. The basin is 16 feet in depth. On the east side there is a sight 

 depression in the rim. The entire length of the mound, includiBg. the 

 two cones, is 53 feet, and the width is 26 feet; the centers of the two 

 cones are 30 feet apart. The space between them is raised abov© the 

 general level, and covered with beaded silica, in which there are tw© 

 small vents that spout during the action of the two large cones. Plate 

 XIV is a view of Cone No. 1 from the west, while in Plate XIVss both 

 the cones are shown, the view being from the east or river side. 



The white and grayish-white geyserite, of which the cones and laoJimdl 

 are composed, is brittle and breaks readily into slab-like masses. Pools, 

 of water are found on the west side of the geyser and on the msm ©one 

 near the pillar-like mass. The erui^tions consist of two well defined 

 columns, alternating with each other, from the two cones, and spurts 

 from the small vents. A large portion of the water is thrown into sprayy 

 which adds to the effect. The water escapes in jets, which average 

 about twenty per minute. 



1870. — The Grotto is mentioned by Langford as spouting to a beight 

 of 60 feet, the eruption lasting an hour.* 



1871. — I did not see the Grotto in action, but Colonel Barlow s.p®aks 

 of its playing several times in the twenty- four hours, t 



1872. — The following eruptions were noted hy me in 1872 : 



Ifo. 



Date. 



Eruption began. 



Dura- 

 tion. 



Maximum hciglit. 



Average leight.. 



1 



Aug. 16 



2.45 p.m 



1.27 p. m 



h. m. 



38 



2 33 



Cone 1 32 feet.. 



Cone 1 33: feet. 





Aug. 19 



Cone 2, 24 feet 





9 



Cone 1 31 feet 









Cone 2, 41 feet. 



Cone 2, IS feet. 









In the second eruption the maximum was attained, in Cone Na 1, I 

 hour and 13^ minutes after the eruption began, and in Cone No. 2,, 2 min- 

 utes later. After the eruption the water sank rapidly until it was out 

 of sight, and everything became perfectly quiet. In the second eraption 

 the maximum height of Cone No. 2 exceede(^ that of Cone No. 1, and the 

 spurt made a fine display, the base of the column being wide, tapering 

 to a point at the top. It was accompanied by considerable steam. In 

 Cone No. 1 the average height was very uniform, and the mass of water 

 thrown up was very much spread out. The eruptions have a .steam 

 period at the close. In the first eruption this was about 3 minutes ; in 

 the last one it was not taken, but it was short. 



In an eruption seen by Mr. Holmes, but not noted, the smalfer cone 

 spurted higher than No. 1, although usually the reverse is the case. 



* Scribuer's Monthly, Vol. II, p. 124. 



tEeconunissauce oftlie Yellowstone Elver in 1871, p. 26. 



