344 FROM FORT HALL TO HEAD OF HELL GATE RIVER. 
as white as loaf-sugar, and reduces to a pulverulent state with the fingers ; in some places it forms 
a bed, though yielding readily to the knife. A pound of this salt was secured, with the intention of 
submitting it to Dr. Evans, the geologist of the expedition, for analysis. The rocks, leaves, grasses, 
and even the ground over which the water from the springs around the base of the mound flows, 
are all covered with a saffron-colored incrustation. The prairie, for some distance around and 
near this mound, is covered with a white incrustation, in some places half an inch thick. The 
springs occur from east by south to west, while none occur towards the north. This mound 
occurs in the middle of the long level prairie before referred to and described, forming a promi- 
nent and well-known landmark. From the peculiar appearance presented by this mound, and its 
exceedingly singular formation, I have supposed it to be an extinct volcano, and the opening on 
the top, now a spring of boiling water, to be its crater. The surface is composed of a substance 
which occurs in concentric layers, varying from one to four inches in thickness, which I supposed 
to have been thrown from the crater in a molten state, and naturally assumed the position of 
the parallel layers, as shown by the formation. Again: the black scoriated rock found on its 
surface gives indubitable evidence of much and excessive heat, and also shows that it was once 
in a molten state. 
The nearest mountains to this mound are six or eight miles distant, thus forming a permanent 
and notable landmark in this large, level, prairie valley. I collected here a number of rich and 
valuable specimens, all of which, together with those already collected, have been submitted to 
Dr. Evans for examination and description. 
January 2, 1854.—Was pleasant, though at times cloudy ; the wind blowing moderately from 
the southwest. We remained in camp to-day on the Deer Lodge creek. 
January 3, 1854.—Commences cloudy, with a very strong wind from the southwest, accompa- 
nied by a heavy fall of rain, which continued till 7 a. m., when it changed to a severe snow- 
storm, and continued with great force till 10 a. m., when it ceased, cleared off, and became an 
exceedingly bright and beautiful day. We resumed our march at 10.30 a. m., which lay along 
the Deer Lodge creek for a mile, when, crossing this creek, it tended down the valley of Deer 
Lodge, by an exceedingly level and beautiful road, for a distance of eighteen miles; our course 
being north 18° west magnetic. In the interval we crossed several mountain streamlets, the waters 
of which were mostly unfrozen. The largest of these streams, coming from the east, is called the 
Race Track creek. Eight miles from our camp of last night we had a fine view up the valley to 
the east, through which flows one of the largest tributaries to the Hell Gate fork of the Bitter 
Root river, whose stream, swollen by the waters of the numerous prairie rivulets and mountain 
streams, running through wide and beautiful meadows, could be traced for many miles by the dark 
line of cotton-wood bordering its banks, which was now two feet deep in the channel, and thirty 
to forty yards wide; while on its banks are also the willow, birch, and black-haw. 
For the greater portion of to-day’s journey, the river flows through a broad prairie valley, the 
northern portion of which is a continuation of the Deer Lodge prairie, which, at a distance of a 
mile from our trail to the left, formed a plateau about two feet above the general level of the valley, 
and extending to the base of the mountains, which continue to be covered with the pine, and their 
peaks with snow. ‘The country to the east, like that on the western portion of the valley, rises 
gradually for a half-mile from the bed of the stream, and with a very gradual slope forms a broad 
plateau, which extends to the base of the mountains, at a distance of eighteen miles, the valley 
diminishing to a width of four miles—the stream then bathing the mountains on the north. Hay- 
ing travelled twenty miles, we encamped on the right bank of the Hell Gate river, two miles 
above the mouth of the Little Blackfoot fork, its principal and largest tributary. Our road to-day 
has been exceedingly level and beautiful, being prairie the whole distance. 
The grass of the valley continues very excellent. The soil to-day is principally of sand, which 
we found mingled with much mica, occurring in small glistening scales. 
During the latter portion of to-day’s march we found the ground covered with two inches 
