GEOLOGICAL SURVEY OF THE TEKKITORIES. 247 



row fissuiGj along which for 6 or 8 feet the water boils constautly. Kear 

 this is a small geyser-iiiound strongly colored with iron. 



On the opposite side of the creek is a broad terrace of the siliceous 

 spring-deposits, npon which stand several siuiill luouiids very ])rettily 

 ornamented, from 1 foot to 2 feet high, whose pools boil considei-ably, and 

 evidently spout occasionally, though no one of them was seen in eru'ptlon. 

 One of these, near the creek and nearly opposite to Minute Man, is 

 shaped like a conch-sheft and strongly colored with iron, and was called 

 Iron-Conch Geyser. 



Nearer the base of the hills, there are several large hot pools. One of 

 them was so well furnished with coralliform masses, standing in the 

 shallow water near its ei]ge, as to be called the Coral Pool. This meas- 

 ured about 40 feet by oO, with a shallow border, and a deep central pit 

 about 10 feet across, from which numerous bubbles of gas were escaj)- 

 ing. There is a strong flow of water of the tem})erature of 1G(P. A. 

 little to the west of this, a valley runs well up into the hills and contains 

 several large boiling pools, but no geysers. One boils with great vio- 

 lence, with a very large escape of steam. The i)ools and old deserted 

 basins extend up the slopes of the hills to elevations of from 100 to 150 

 feet above the creek. 



As a whole, these springs and geysers show far greater amounts of 

 sulphur, and especially of iron, in their deposits than any of those on the 

 Madison. The geysers also show much greater irregularities of erup- 

 tions. The group seems to me, as a whole, younger than those in the 

 Fire-Uole Basins. The litthi geysers on the west side of the creek are 

 plainly young, and are just beginning mounds which promise to attain 

 consiclerable size. 



On the east side of the creek, between it and the lakes, we find a clus- 

 ter of ragged hills, separated by crateriform hollows and valleys, which 

 are occupied more or less completely by mud-springs and sulphur-vents. 

 Upon breaking up the surface-crust about these latter, we tindall its 

 hollows lined with sulphur, either in distinct crystals or in moss-like 

 aggregations of imperfect ones. Upon first observing the shape and 

 contents of these hollows, one would naturally suppose them to be old 

 volcanic craters, whose connections with the interior fires were becom- 

 ing nearly stopped up ; but, upon more careful examination, it becomes 

 evident that they have been hollowed out of the surrounding sandstone 

 by the action of the hot springs themselves, which have disintegrated 

 and removed portions of the sandstone and conglomerate of the old 

 lake-terrace. Worn bits of rocks, penetrated by numerous small irreg- 

 ular holes, are abundant on all the lower parts of the slopes, as well as 

 about the existing vents, showing that the process is still going on. 

 These springs are evidently much affected by variations in the sup[)ly, 

 of water. Manv which were entirelv <lrv uave abundant evidence timt 

 they sometimes give forth considerable streams. The effects of these 

 variable supplies upon the activity of the ditferent sjjrings and geysers 

 are probably very ditferent in different cases. Since a full basin seems 

 to be essential to an eru[)tion, a greater supply of water to fill the place 

 of that ejected would, in numy cases, cause more frequent and powerful 

 eruptions. On the other hand, it is probable that too large a supply, 

 causing a continuous stream to i)ass through anil escape from the basin 

 of a geyser, would cool down its contents below the temperature essen- 

 tial to an eruption. 



The springs extend eastward along the shore of the lake for several 

 miles near its i)resent level, and some were seen boiling up from its 

 bottom, several yards from shore. Many occur also in the marsh about 



