250 EEPOET UNITED STATES GEOLOGICAL SURVEY. 



Captain De Lacy, however, did not visit the geyser basin himself, as 

 the following- extract from his article in Contributions to the Historical 

 Society of Montana (page 130) will show : 



They Ithe party that Jeft them^ passed Lake Lewis and came to the foot of the large 

 lake, where they found our old camp. Here they went up on the west side of the lake 

 to its head, and there found a number of hot springs, some of which were geysers, 

 which they saw in action, spouting up the water to a great height, and thence went 

 over to the South Fork of the Fire Hole River, where they again saw our camps, and 

 thence down the Madison River to Virginia City. These facts I obtained afterward 

 at Bannock City from Mr. Charles Ream, one of the party, and it was thus established 

 "conclusively that the largo lake was the head of the South Snake, and I was enabled, 

 to correct the course of the Madison River, and correct my surveys with it. 



The lake which we had now discovered was the lake afterward called De Lacy's 

 Lake on the United States surveyor-general's map of the Territory, and afterward re- 

 named Shoshone Lake by Dr. Hayden, and the lake below it was the one called by 

 him Lewis Lake.* 



General Meredith, surveyor- general of Montana in 1867, named tlie 

 lake De Lacy's Lake, and it was so called on several editions of a map 

 issued by the Messrs. Colton, of New York.t Captain De Lacy is mis- 

 taken in thinking that Dr. Hayden renamed it, as Prof. F. H. Bradley 

 did so, and gives as reasons for so doing the fact that the position on De 

 Lacy's map does not correspond, and that there are numerous other 

 errors.J Ko matter what name the lake may be known by hereafter, the 

 Geyser Basin will be known as the Shoshone Basin, the name given by 

 Professor Bradley, who was the first person to give anything like a 

 detailed description of its springs and geysers. The principal geysers 

 were named by him. The general elevation of thii^ geyser basin is 7,825 

 feet, and the theoretical boiling point is between 198° F. and 199° F. 

 The slopes of the plateau surrounding the lake are all very heavily tim- 

 bered. 



Geology. — The geology of the region of the Shoshone Geyser Basin is 

 exactly like that of the Geyser Basin of Fire Hole Eiver. Ehyolitic 

 rocks form the main mass of .the plateau, the summits being composed 

 of black and brown obsidian. In various parts of the basin there are 

 remnants of a sandstone, which seems to be composed of particles of 

 obsidan and broken-up geyserite. In some places it appears vitrified, 

 as though it had become permeated with the siliceous waters from the 

 springs. The marsh below the springs has a number of steam vents 

 and old springs. It is^probable that this marsh is sometimes overflowed 

 by the lake. Six or eight of the springs in the marsh are easily recog- 

 nized, but were inaccessible at the time of our visit. 



Shoshone Creek is a rapid stream, some 10 to 15 feet in width, which 

 flows from north to south through the basin. The temperature of its 

 water opposite the Yellow Crater Group was 70° F., and below the 

 mouth of Fall Creek, below all the springs, it was 80° F. 



* On pages 142, 143, of the article from which this extract is iaken, Captain De Lacy 

 says: ''I never claimed that my map was correct in all particulars, or that I had been 

 entirely over the region in question. Outside of the surveys and my own explorations 

 I was obliged to rely on the reports of others who had beeu there hunting or explor- 

 ing, and these were not always accurate. I put down what I considered the best, 

 hoping to be able to improve the map every year, and make it thoroughly correct 

 finally. I do claim, however, that I was the first to publish the fact that the South 

 Snake River took its rise in a large lake north of Lake Jackson and flowed into it — 

 a fact confirmed by Dr. Hayden's own surveys — and this would authorize me, accord- 

 ing to the general rules governing geographers, to name it myself, or for others to 

 give it my name." 



t Historical Society of Montana, Vol. I, page 141. 



t Report U, S. Geol, Survey, 1872, page 244. 



