168 GEYSERS. 
the past nine summers in a study of its geysers and hot springs. To 
many readers this region is doubtless familiar. The geysers are found 
in detached groups, occupying basins or valleys of the great table-land 
which forms the central portion of the park, a region whose heavy 
forests and uninviting aspect, combined with the rugged nature of the 
encircling mountain ranges, so long proved a barrier to exploration 
even to those adventurous trappers and prospectors of the Great West, 
and deferred the discovery of this marvellous region until so recent a 
date as 1869. 
The geyser “basins,” as the localities are termed, conform, in their re- 
lations to the surrounding high ground and their coincidence with lines 
of drainage and the loci of springs, to the laws governing the distribu- 
tion of the same phenomena in other parts of the world. The park itself 
is a reservation of about 3,500 square miles, the central portion being an 
elevated volcanic plateau, accentuated by deep and narrow canons and 
broad gentle eminences, and surrounded by high and rugged mountain 
ranges. This central portion, whose average elevation is about 8,000 
feet above the sea, embraces all the hot-spring and geyser areas of the 
park. The volcanic activity that resulted in the formation of the park 
plateau may be considered as extinct, nor are there any evidences of 
fresh lava flows. Yet, the hot springs so widely distributed over the 
plateau are convincing evidence of the presence of underground heat. 
There is no doubt that the waters derive their high temperature from 
_the heated rocks below, and that the origin of the heat is, in some way, 
associated with the source of voleanic energy. 
The various geyser basins, or jfire holes, as they were called by the 
first explorers, each possess individual peculiarities which give charac- 
ter and interest to each locality. The most noted of these “basins” is 
however that known as the Upper Geyser Basin of the Firehole River, 
one of the headwaters of the great Missouri. This “‘ Upper Basin,” as it 
is generally called, lies a little westward of the center of the park, and 
is reached by a ride of some 50 miles, over excellent roads, from the 
railroad terminus. It is a valley of 14 miles long by one-half mile 
broad, inclosed by the rocky cliffs or darkly wooded slopes of the great 
Madison Plateau, and drained by the Firehole River, along whose 
banks the largest geysers are situated. The whole floor of the valley 
is fairly riddled with springs of boiling water, whose exquisite beauty 
is indescribable. Light clouds of fleecy vapor curl gently upward from 
waters of the purest azure or the clearest of emerald, and, encircling 
rims of white marble-like silica, form fit setting for such great gems. 
A large part of the valley floor is covered with the white deposit of silica 
known as siliceous sinter, deposited by the overflowing hot waters.* 
The weird whiteness of these areas, the gaunt white trunks of pine trees 
killed by the hot waters, the myriad pools of steaming crystal, and the 
*See “Formation of Hot Spring deposits,” W. H. Weed Ninth Ann. Rept. Director 
U.S. Geological Survey, 1889. 
