92 EEPORT UNITED STATES GEOLOGICAL SURVEY. 



Yellow Stilphur Spring (Plate VI &). — This is the principal spring of 

 the group, and the one that first claims the attention of every visitor, as 

 it is characterized by the escape of great volumes of steam and is gen- 

 erally in Adolent ebullition. Dr. Hayden, in the report for 1871 (p. 89), 

 thus describes this spring : 



On the south side of these hills, close to the foot, is a magnificent sulphur spring. 

 The deposits around it are silica ; but some places are white, and enameled like the 

 finest porcelain. The thin edges of the nearly circular rim extend over the waters of 

 the basin several feet, yet the open portion is 15 feet in diameter. The water is in a 

 constant state of agitation. The stream that issues from this spring is so strong and 

 hot that it was only on the windward side that I could approach it and ascertain its 

 temperature, 197°. The agitation seemed to affect the entire mass, carrying it up im- 

 pulsively to the height of four feet. It may be compared to a huge caldron of per- 

 fectly clear water somewhat superheated. But it is the decorations about this spring 

 that lent the charm, after our astonishment at thrf seething mass before us — the most 

 beautiful scalloping around the rim, and the inner and outer surface covered with a 

 sort of pearl-like bead-work. The base is the pure white silica, while the sulphur 

 gave every possible shade, from yellow to the most elegant cream. No kind of em- 

 broidering that human art can conceive or fashion could equal this specimen of the 

 cunning skill of nature. 



In 1870 Lieutenant Doane observed it^ and speaks of it in his report 

 as follows : 



It measures 15 by 20 feet on the inside. The water boils up constantly from 3 to 7 

 feet in height, the whole surface rising and falling occasioually with a flux and reflux 

 of 4 feet additional, overflowing its basin and receding every few minutes. The basin 

 is built up with a solid rim or lining of pure crystalline sulphur (?) 4 feet in width all 

 around the edge, probably amounting to 40 tons in weight. The water is clear, but 

 of a whitish cast, and above the boiling point, steam being evolved from its surface. 

 The basin cannot be approached nearer than 20 feet distant on account of the scalding 

 vapors. A small channel leads down the slope, and for several hundred feet its bed is 

 incrusted with a sulphur deposit, showing that the spring occasionally flows a con- 

 siderable quantity of water. The deposit is from 3 to 10 inches deep. 



In Dr. Hayden's description the temperature is given as 197°. The 

 same year I found it to be 183^°, which is the temperature obtained by 

 Mr. Schonborn and placed on his chart in the report for 1871. In 1872 

 the temperature obtained was 1780F. These variations are due partly 

 to the fact of differences in the spring at different times and partly to 

 the fact that the temperature at the edge is different from what it is in 

 the center. We passed the spring in 1878 and found that it presents 

 the same characters it did in 1871 and 1872. The steam jet, however, 

 which we noticed in 1871 and 1872 quite close to this spring did not 

 appear to be in action. 



Turhicl Blue Mud Spring. — This is near the Large Suljjhur Spring, and 

 in 1871 had a temperature of 164° F., and in 1872 163o F. It has a 

 basin about 35 feet in diameter, and its contents are rather thin muddy 

 water than mud. It is acid in reaction, and tastes of alum. 



South of the springs just described is a basin filled with innumerable 

 mudpuffs, sulphur holes, and steam-vents. Lieutenant Doane, on page 

 16 of his report, thus describes them : 



The mud ejected is of different degrees of consistency, but generally about the thick- 

 ness of common mortar, and mostly of an iron-brown color. It boils slowly like niish, 

 with bubbles of gas escaping, and is spouted to various heights, from 2 to 40 feet, falling 

 with dull splashes around the edges of the craters, which are being built up continually 

 and continually caving in, to be worked over and ejected as before. Some of the 

 springs throw up yellow mud, others white, and a few pink. The different springs 

 of all classes had no appai'ent connection with each other, though often but a few 

 feet apart ; the mud being of different colors, the basins having difl'erent levels, and 

 the pulsations being independent, one being frequently in violent ebullition while 

 another near by was quiescent. A plasterer would go into ecstacies over this mortar, 

 which is worked to such a degree of fineness that it can be dried in large lumps, either 

 in the sun or in a fire, without a sign of cracking, and, when once dry, is a soft, finely- 



