Coming one day in sight of a magnificent elk, he took careful aim at the unsuspecting animal and fired. To his great amazement, the elk not only was not wounded, but seemed not even to have heard the report of the rifle. Bridger drew considerably nearer and gave the elk the benefit of his most deliberate aim; but with the same result as before. A third and a fourth effort met with a similar fate. Utterly exasperated, he seized his rifle by the barrel, resolved to use it as a club since it had failed as a firearm. He rushed madly toward the elk, but suddenly crashed into an immovable vertical wall which proved to be a mountain of perfectly transparent glass, on the farther side of which, still in peaceful security, the elk was quietly grazing. Stranger still, the mountain was not only of pure glass, but was a perfect telescopic lens, and, whereas, the elk seemed but a few hundred yards off, it was in reality twenty-five miles away! Another of Bridger's discoveries was an ice-cold spring near the summit of a lofty mountain, the water from which flowed down over a long smooth slope, where it acquired such a velocity that it was boiling hot when it reached the bottom.[U] [U] This story, which is taken from the report of Captain W. F. Raynolds, was one of Bridger's favorites, and it is even said that he did not regard it as pleasantry at all, but as plain matter of fact. Mr. Langford, who often heard him relate it, says that he generally described the stream as flowing over the smooth surface of a rock, and reasoned that, as two sticks rubbed together produce heat by friction, so the water rubbing over the rock became hot. In proof, he cited an instance where the water was hot only in close proximity to the rock and not at the surface. Mr. Langford found a partial confirmation of the fact, but not of the theory, in fording the Firehole River in 1870. He passed over the smooth deposit of an active hot spring in the bed of the stream, and found that the stream bottom and the water in contact with it were hot.