Classed with reference to their chemical constituents, the springs here and elsewhere in the Yellowstone Valley are of two kinds: those in which lime predominates, and those in which silica is most abundant. The springs of Gardiner's River are mainly the former. Where does the lime come from? The geology of the country surrounding the springs shows already that there is underneath the spring deposits, at least a thickness of 1,500 feet, of carboniferous limestone; and if the origin of the heat which so elevates the temperature of the waters of these springs is as deep seated as is generally supposed, the heated waters have ample time and space for dissolving the calcareous rocks through which they flow.
About a mile above the springs, Gardiner's River separates into three branches--the East, Middle, and West Forks, which rise high up in the mountains, among perpetual snows. They wind their way across a broad plateau covered mostly with a dense growth of pines, but with some broad, open, meadow-like spots, which, seen from some high mountain peak, lend a rare charm to the landscape. After gathering a sufficient supply of water, they commence wearing their channels down into the volcanic rocks, deeper and deeper as they descend. Each one has its water-fall, which would fill an artist with enthusiasm. From the high ridge between the East and Middle Forks a fine view is obtained of the surrounding country.
Far to the southwest are lofty peaks covered with snow, rising to the height of 10,000 feet, and forming a part of the magnificent range of mountains that separates the Yellowstone from the sources of the Gallatin. From this high ridge one can look down into the chasm of the Middle Fork, carved out of the basalt and basaltic conglomerates to the depth of 500 to 800 feet, with nearly vertical sides. In the sides of this cañon, as well as those of the East Fork, splendid examples of basaltic columns are displayed, as perfect as those of the celebrated Fingal's Cave. They usually appear in regular rows, vertical, five and six sided, but far more sharply cut than elsewhere seen in the West, though occasionally the columns are spread out in the form of a fan. Sometimes there are several rows, usually about fifty feet high, one above the other, with conglomerate between.