PKALE.] HAYDEN'S valley SPEINGS MUD VOLCANOES. 95 



the river. In some places these sandstones appear to have been infil- 

 trated with the siliceous waters which has given them a vitreous appear- 

 ance. Above these sandstones are finer-grained ones, as shown at the 

 Grotto (No. 12.), and on the surface are clays. When the water passes 

 through these we have the mud springs. When it emerges from the 

 sandstones it is clear, as in the Grotto, or simply turbid as in some of the 

 springs near the river's edge. As I pointed out in my report for 1871 

 (page 181), the dilference in the springs is due to the character of the 

 rock through which the water has to pass. 



Every possible variation is to be found in the contents of the mud 

 pots ; some are simply muddy water, others are like kettles of boiling 

 soap ; some like caldrons of mush or paint, and still others like stiff 

 mortar. The supply of water has a great deal to do with the consist- 

 ency of the mud. In a wet season, when the surface supply is greater, 

 the mud will be thinner. It is of all colors — red, pure white, like meer- 

 schaum when it is dried, lavender, gray, or blue. Nearly all the springs 

 give off sulphuretted hydrogen, and silver watches carried by members 

 of the party soon showed the effect of the sulphurous gases. The quiet 

 pools are generally sulphur pools, some of them of large dimensions. 

 Besides the springs there are many steam vents, whose holes are lined 

 with sulphur crystals. The mud volcanoes have generally a circular pit 

 about 10 feet deep, with a rim or mound on the outside raised several feet 

 above the general level. Such a spring may begin simply as a clear 

 spring, into which the earth falls. The steam gradually works this up 

 with the water, and it is a mud spring. It may become thicker by the 

 caving in of the sides, although the evaporation of the water is the 

 canse in most of the cases. After a time the spring may become choked, 

 and we have one of the many dead holes seen among the active springs. 



I shall now give full descrii^tions of the three principal springs, which 

 are the Geyser, the Mud Volcano, and the clear boiling or pulsating 

 spring (Grotto). The rest of the springs will be given in a table follow- 

 ing, in which a few additional points will be given briefly. 



Mud Geyser (Plate Vic). — This is the principal object of interest at 

 the mud springs locality, and is easily recognized by its depressed ba- 

 sin, which measures 150 feet by 200 feet, and is 8 feet deep. In this the 

 basin proper, or crater of the geyser is about 60 feet in diameter, sur- 

 rounded by a rim that slopes inward at an angle of 30° to a funnel- 

 shaped orifice. This is seen projecting above the water in the picture 

 (Plate Vic), just to the right of the fountain-like mass. Between this 

 crater and the rim of the outer basin there is a deposit of clay and silica 

 which has hardened and resembles a very fine clay-slate. It has been 

 deposited by the water of the geyser. The outer rim is broad and mound- 

 like, and has a channel cut through it by which any surplus water is 

 carried from the basin, although ordinarily there is no overflow from the 

 geyser. This is shown in the foreground of the illustration. On the 

 west side of the basin, near the crater, there is a steam vent, and in the 

 south end two springs, or spring-basins, for there are numerous springs. 

 W^hen the outer basin is filled, the outlines of these springs as well as 

 that of the geyser crater are not distinguishable. These springs appear 

 to be perfectly iudei)endent of the geyser in their action. 



In order to show the changes that have taken place in the geyser since 

 it was first described, I will present the characteristics described each 

 year. 



1870. — Lieutenant Doane describes this geyser in his report and gives 

 a]i account of its eruptions, as follows: 



This was a periodic geyser, liavin<j eruptions every six hours, and iu the following 

 manner : The crater being full of boiling water, and the vapor vent active, suddenly 



