"The climate during the months of June, July, and August, in this valley, cannot be surpassed in the world for its health-giving powers. The finest of mountain water, fish in the greatest abundance, with a good supply of game of all kinds, fully satisfy the wants of the traveller, and render this valley one of the most attractive places of resort for invalids or pleasure-seekers in America." From the summit of the ridge the party descended to the valley of the Yellowstone, nearly opposite the mouth of the East Fork of that river. The road was a rough one. During the period of volcanic action in this region, the sedimentary rocks were crumpled into high, sharp, wave-like series of ridges; from innumerable fissures, igneous matter was poured out over the surface cooling into basalt; and from volcanic vents was also thrown out, into the great lake, rock fragments and volcanic dust, which were arranged by the water and cemented into a breccia. Deep into these ridges the little streams have cut their channels, forming what should be called valleys, rather than cañons, with almost vertical sides. These ravines, 500 to 800 feet deep, covered mostly with grass or trees, occur in great numbers, many of them entirely dry at present, but attesting the presence and power, at no very remote period, of aqueous forces compared with which those of the present are utterly insignificant. Before studying this portion of the Yellowstone Valley, it may be well to retrace our steps to the mouth of Gardiner's River, to explore the Third Cañon of the Yellowstone, so far as possible, and the rest of its interesting valley up to this point.