haoot.] THE GEYSER BASINS. 355 



UPPER GEYSER BASIN. 



At the Riverside geyser the road crosses the Firehole river by a 

 bridge, which is generally regarded as marking the entrance to the 

 Upper Geyser basin. The basin measures about two and one-halt* miles 

 in length and one and one-quarter miles in width, and contains the 

 greatest number and, with the exception of the Excelsior, the largest 

 geysers in the park. At the Grand geyser, a central point, the eleva- 

 tion is 7,200 feet above sea level. Like the Norris and Lower Geyser 

 basins it occupies a depressed area in the rhyolite lavas, with ridges 

 rising Tiiore or less abruptly on all sides, the .Madison plateau on the 

 west presenting a bold escarpment. The Firehole river extends the 

 entire length of the basin, and with its tributaries drains the region. 

 The basin lies within 5 miles of the continental water-shed which sep- 

 arates the Atlantic from the Pacific drainage. The lowest passes 

 between the two are not more than 800 feet above the basin, and the 

 line of the Continental Divide makes a sharp bend and loop to the 

 southeast in order to inclose the drainage area of the Firehole on the 

 Atlantic side. 



There are between 46 and 50 geysers in the Upper basin, and nine 

 of them maybe regarded as gvysevs of the first order. The Giant, 

 Giantess, Grand, Splendid, Grotto, Castle, Beehive, Oblong, and Old 

 Faithful are found within a few hundred yards of the river and within 

 easy walking distance from the hotel, which is situated near Old Faith- 

 ful. While the geysers present much in common, each offers distinc- 

 tive features in the display of the water thrown out, the quantity dis- 

 charged, the duration of explosive energy, and in the intervals between 

 eruptions. The height of the column of water in these large geysers 

 varies from 00 to L'oO feet. Old Faithful is the most regular, with inter- 

 vals averaging sixty-five minutes, throwing a column of water vary- 

 ing from 00 to 150 feet. The Giantess issues from a deep, funnel- 

 shaped pool. The (Jiant has built up a sinter cone 10 feet in height. 

 The Castle breaks out from the top of a series of sinter terraces. The 

 Grand presents a quiet, shallow basin on the level with the sinter plain. 

 The Splendid issues from an unpretending pool not unlike hundreds 

 of hot springs in the park. Black Sand and Emerald springs afford 

 excellent Opportunities for a study of algous growths in hot waters. 

 There is a most interesting group of springs and geysers, seldom seen 



by tourists but well worth a visit, on Iron creek, a tributary of the 

 Firehole. 



Plate II represents Old Faithful in action. It is a tine exhibition 

 of the geyser, which is seen to the best advantage on a calm day, the 

 absence of all wind permitting the water to fall freely in a perpendicular 

 column broken up into graceful arrow-shaped bodies. The water column 



