_The Gardiner Cañon_ is a precipitous valley of loose gray walls suggestive of danger from falling rocks. The nests of fish-hawks here and there crown detached pinnacles. The most striking feature of the cañon is the river, a typical mountain torrent of such rapid fall over its rocky bed that it is a continuous succession of foaming cascades. Some four miles up the river, at the point where the road leaves it, the tourist gets his first sight of any indication of subterranean heat. This is a large stream of hot water, in early times called the _Boiling River_, issuing from an opening in the rocks and emptying directly into the river. It is formed of the collected waters of Mammoth Hot Springs which find their way to this point through underground passages. It was here that "numbers of invalids" were encamped when Hayden and Barlow saw the spot in 1871. From the last crossing of the Gardiner a winding road, which rises 600 feet in its length of one mile, brings the tourist to the world-renowned _Mammoth Hot Springs_, and to the administrative and business headquarters of the Park. [Illustration: _Terry Engr. Co._ _U. S. Geological Survey of the Territories._ Mammoth Hot Springs. Bunsen Peak in the distance.] [Illustration: _U. S. Geological Survey of the Territories._ Pulpit Terrace.] First in importance, among the many points of interest accessible from this locality, are the _Hot Springs Terraces_. These have been built one upon another until the present active portion constitutes a hill rising 300 feet above the site of the Mammoth Hot Springs Hotel. The formation about these springs, it will be remembered, is calcareous, and to this fact is due its distinctive character, so different from the silica formations which prevail nearly every-where else in the Park. The overhanging bowls which these deposits build up are among the finest specimens of Nature's work in the world, while the water which fills them is of that peculiar beauty to be found only in thermal springs. Speaking of this feature Dr. Hayden says: "The wonderful transparency of the water surpasses any thing of the kind I have ever seen in any other portion of the world. The sky, with the smallest cloud that flits across it, is reflected in its clear depths, and the ultramarine colors, more vivid than the sea, are greatly heightened by constant, gentle vibrations. One can look down into the clear depths and see, with perfect distinctness, the minutest ornament on the inner sides of the basins; and the exquisite beauty of the coloring and the variety of forms baffle any attempt to portray them either with pen or pencil."[AZ] [AZ] Page 69 Hayden's Report for 1871. See Appendix E.