PEALE.] UPPER GEYSER BASIN GROTTO GROUP. 193 



further mention than is made in the table. Crossing to the east side 

 we find two geysers, viz., the Fan and the Eiverside. 



No. 21. Fan Geyser (Plate XV). — The Fan Geyser was so named by 

 the party of 1870 because the water during the eruption spreads out in 

 fan-shaped jets, from the fact that there are two craters, the streams 

 from which cross each other. These two craters have orifices of about 

 2 feet diameter each, and just below them is a steam vent called the 

 "perpetual spouter," which sometimes acts in concert with the Fan. 

 The crater of the geyser is composed of pink geyserite, which rises from 

 the river in a series of rounded masses which are beaded with silica. 



1870. — Langford describes the erui)tion of the Fan as follows: 



The Fan has an orifice which discharges two radiating jets of water to the height 

 of 60 feet, the falling drops and spray resembling a featlier fan. It is very beautiful. 

 Its eruptions are very frequent, lasting usually from 10 to 30 minutes. A vent con- 

 nected with it, about'40 feet distant, expels dense masses of vapor 50 or 60 feet high, 

 accompanied by loud, sharp reports during the time the geyser is in action.* 



Lieutenant Doane, speaking of the same geyser, says : 



First, the steam would rush from the upper crater, roaring violently, then this 

 would suddenly cease, to be followed by a fan-like jet of water rising from the lower 

 crater to the height of over 40 feet, often playing for perhaps two minutes ; then this 

 would suddenly stop flowing, and the steam would rush forth again for a time. Oc- 

 casionally the small crater threw a transverse stream, sometimes alternating with 

 either of the others; and thus they played on for hours, alter which all would sub- 

 side to a gentle bubbling.t 



1871. — I did not see the Fan in action in 1871, nor were any notes 

 concerning it obtained by the other members of the party. 



1872. — I did not see the Fan in action in 1872, but Professor Bradley 

 did, and has the following : 



When Fan Geyser was in full eruption its partner, 30 yards off, was steaming 

 gently. Fan stopped for a moment, and its partner fairly roared with a rush of steam, 

 which stopped as soon as Fan ojDened again. Yet they are not in full sympathy; for 

 on anoiher occasion Fan was steaming or boiling very gently, while its partner was 

 boiling furiously and throwing water 5 or 10 feet high, but with quiet intervals, dur- 

 ing which Fan showed no access of force. (Under such circumstances, one is inclined 

 to question whether Fan's partner may not possibly serve as the vent for two distinct 

 geyser-tubes.) t 



These notes were taken mainly for the purpose of determining the 

 sympathy, and do not give any facts as regards the interval or duration. 



1873. — Professor Comstock saw the Fan in action and describes the 

 eruption as follows : 



This began at 2.43 p. m., almost precisely at the moment when the eruption began 

 in the Riverside. Gradually increasing in intensity, it was throwing a large column of 

 water at 2.49 p. m., Avhich continued, but gradually diminishing, until 2.45 p. m., at 

 which time it almost ceased, spluttering occasionally, however, until 2.56 p. m. This 

 record shows a remarkable similarity or sympathy between, the Fan and the Riverside. 



1877. — General Sherman's party saw the Fan in action, but give no 

 particulars. 



1878. — I saw but one eruption of the Fan, which occurred September 

 11. Tlie following are the notes : 



First spurt at 12.13 p. m. ; stopped suddenly in 2 minutes 10 seconds. 



Second spurt at 12^. 15"'. 40« p. m.; stopped at the end of 2 minutes 

 25 seconds. 



Third spurt at 12'». 18™. 35^ p. m.; stopped at the end of 25 seconds. 



•Scribner's Monthly, Vol. II., 1871, p. 123. 

 t Yellowstone Expedition of 1870, p. 31. 

 I Report U. S. Gcol. Survey of the Terr., 1872, p. 236. 

 13 H, PT II 



