Such is the somewhat fanciful view which Captain Bonneville gives to this great body of water.  He has evidently taken part of his ideas concerning it from the representations of others, who have somewhat exaggerated its features.  It is reported to be about one hundred and fifty miles long, and fifty miles broad.  The ranges of mountain peaks which Captain Bonneville speaks of, as rising from its bosom, are probably the summits of mountains beyond it, which may be visible at a vast distance, when viewed from an eminence, in the transparent atmosphere of these lofty regions.  Several large islands certainly exist in the lake; one of which is said to be mountainous, but not by any means to the extent required to furnish the series of peaks above mentioned.

Captain Sublette, in one of his early expeditions across the mountains, is said to have sent four men in a skin canoe, to explore the lake, who professed to have navigated all round it; but to have suffered excessively from thirst, the water of the lake being extremely salt, and there being no fresh streams running into it.

Captain Bonneville doubts this report, or that the men accomplished the circumnavigation, because, he says, the lake receives several large streams from the mountains which bound it to the east.  In the spring, when the streams are swollen by rain and by the melting of the snows, the lake rises several feet above its ordinary level during the summer, it gradually subsides again, leaving a sparkling zone of the finest salt upon its shores.

The elevation of the vast plateau on which this lake is situated, is estimated by Captain Bonneville at one and three-fourths of a mile above the level of the ocean.  The admirable purity and transparency of the atmosphere in this region, allowing objects to be seen, and the report of firearms to be heard, at an astonishing distance; and its extreme dryness, causing the wheels of wagons to fall in pieces, as instanced in former passages of this work, are proofs of the great altitude of the Rocky Mountain plains.  That a body of salt water should exist at such a height is cited as a singular phenomenon by Captain Bonneville, though the salt lake of Mexico is not much inferior in elevation.

To have this lake properly explored, and all its secrets revealed, was the grand scheme of the captain for the present year; and while it was one in which his imagination evidently took a leading part, he believed it would be attended with great profit, from the numerous beaver streams with which the lake must be fringed.

This momentous undertaking he confided to his lieutenant, Mr. Walker, in whose experience and ability he had great confidence.  He instructed him to keep along the shores of the lake, and trap in all the streams on his route; also to keep a journal, and minutely to record the events of his journey, and everything curious or interesting, making maps or charts of his route, and of the surrounding country.