of the Yellowstone and Firehole Rivers. 113° 
The springs, which are now in active operation, are only a few 
out of hundreds which once covered the entire area, but which 
are now dead or dying ou 
e two groups, which I will notice next, are called the Sul- 
pee and Mud Springs (see the accompanying charts). The 
argest group is found on the east side of the Yellowstone, at 
Crater Hills, eight miles below the Lake. This district covers 
an area of about half a mile square, and is sometimes called the 
“Seven Hills,” from the fact that there are here several mounds 
of siliceous deposits from extinct springs, varying in height from 
50 to 150 feet. The old craters of dead and dying springs, and 
the immense quantity of the siliceous deposits, show that the pre- 
sent active springs represent only the last stages of what must 
have been at some period in the past a magnificent group. Even 
those which now remain excite int tonisl t l around 
the base and high up on the sides of the hill are numbers of 
vents from which steam is constantly issuing, and around the 
edges and inside the orifices a layer of sulphur of the most 
brilliant yellow color has been precipitated. On the west side, 
one of these jets produces a sound like that-of a locomotive, whic 
can be heard for a long distance. The surface is fairly riddled 
with little steam vents, and the crust sends forth a hollow sound 
beneath the tread; and on removing this shelly covering at an 
point, hot vapors come forth, while its under surface is encrusted 
spring is a marvel of beauty. It is composed of silica, but 
scolloped and covered over with the most delicate bead-work, 
and upon the pure white silica is deposited a thin layer of sul- 
phur of the most delicate cream color. One large quiet turbid 
wi 
stream that flows from this group of springs is called Alum ' 
Am. Jour. Sct.—Turrp Series, Vor. II, No. 14.—Fss., 1872 
8 
