In a line with the mountains the plain is gashed with numerous and dangerous chasms, from four to ten feet wide, and of great depth.  Captain Bonneville attempted to sound some of these openings, but without any satisfactory result.  A stone dropped into one of them reverberated against the sides for apparently a very great depth, and, by its sound, indicated the same kind of substance with the surface, as long as the strokes could be heard.  The horse, instinctively sagacious in avoiding danger, shrinks back in alarm from the least of these chasms, pricking up his ears, snorting and pawing, until permitted to turn away.

We have been told by a person well acquainted with the country that it is sometimes necessary to travel fifty and sixty miles to get round one of these tremendous ravines.  Considerable streams, like that of Godin’s River, that run with a bold, free current, lose themselves in this plain; some of them end in swamps, others suddenly disappear, finding, no doubt, subterranean outlets.

Opposite to these chasms Snake River makes two desperate leaps over precipices, at a short distance from each other; one twenty, the other forty feet in height.

The volcanic plain in question forms an area of about sixty miles in diameter, where nothing meets the eye but a desolate and awful waste; where no grass grows nor water runs, and where nothing is to be seen but lava.  Ranges of mountains skirt this plain, and, in Captain Bonneville’s opinion, were formerly connected, until rent asunder by some convulsion of nature.  Far to the east the Three Tetons lift their heads sublimely, and dominate this wide sea of lava—­one of the most striking features of a wilderness where everything seems on a scale of stern and simple grandeur.

We look forward with impatience for some able geologist to explore this sublime but almost unknown region.

It was not until the 25th of April that the two parties of trappers broke up their encampments, and undertook to cross over the southwest end of the mountain by a pass explored by their scouts.  From various points of the mountain they commanded boundless prospects of the lava plain, stretching away in cold and gloomy barrenness as far as the eye could reach.  On the evening of the 26th they reached the plain west of the mountain, watered by the Malade, the Boisee, and other streams, which comprised the contemplated trapping-ground.

The country about the Boisee (or Woody) River is extolled by Captain Bonneville as the most enchanting he had seen in the Far West, presenting the mingled grandeur and beauty of mountain and plain, of bright running streams and vast grassy meadows waving to the breeze.