Evidences of ancient volcanic action on the grandest scale are so abundant and striking throughout the lake basin, that it has been looked upon as the remains of a mammoth crater, forty miles across. It seems, however, to have been rather the focus of a multitude of craters. "It is probable," says the United States geologist, Dr. Hayden, with his usual caution, "that during the Pliocene period the entire country drained by the sources of the Yellowstone and the Columbia was the scene of volcanic activity as great as that of any portion of the globe. It might be called one vast crater, made up of a thousand smaller volcanic vents and fissures, out of which the fluid interior of the earth, fragments of rock and volcanic dust, were poured in unlimited quantities. Hundreds of the nuclei or cones of these volcanic vents are now remaining, some of them rising to a height of 10,000 to 11,000 feet above the sea. Mounts Doane, Longford, Stevenson, and more than a hundred other peaks, may be seen from any high point on either side of the basin, each of which formed a centre of effusion."
All that is left of the terrific forces which threw up these lofty mountains and elevated the entire region to its present altitude, now finds issue in occasional earthquake shocks, and in the innumerable hot springs and geysers, whose description makes up so large a portion of this book of wonders. Nowhere else in the world can the last-named phenomena be witnessed on so grand a scale, in such limitless variety, or amid scenes so marvellous in beauty, so wild and unearthly in savage grandeur, so fascinating in all that awes or attracts the lover of the curious, the wonderful, the magnificent in nature.
In their exploration of the headwaters of the Missouri in the summer of 1805, the heroic Captains Lewis and Clarke discovered and named the three terminal branches of that river--the Jefferson, the Madison, and the Gallatin; then ascending the first named to its springs among the Rocky Mountains, they crossed the lofty ridge of the divide and pursued their investigations along the Columbia to the sea. The following summer they returned, separately exploring the two main branches of the Great River of the Northwest, each perpetuating the name and fame of his brother explorer by calling a river after him. Ascending the southern, or Lewis Fork, Captain Clarke recrossed the mountains to Wisdom River, (a branch of the Jefferson,) then traversed the country of the Jefferson, the Madison and the Gallatin to the Rochejaune, or Yellowstone, which he followed to its junction with the Missouri, where he rejoined Captain Lewis. The map of the country explored by these brave men, makes the source of the Yellowstone a large lake, doubtless from information received from the Indians, but they seem to have heard nothing of the marvels along the upper reaches of the river and around the lake from which it flows.