As soon as the camp was formed, I set about endeavoring to repair my barometer. As I have already said, this was a standard cistern barometer, of Troughton’s construction. The glass cistern had been broken about midway; but, as the instrument had been kept in a proper position, no air had found its way into the tube, the end of which had always remained covered. I had with me a number of vials of tolerably thick glass, some of which were of the same diameter as the cistern, and I spent the day in slowly working on these, endeavoring to cut them of the requisite length; but, as my instrument was a very rough file, I invariably broke them. A groove was cut in one of the trees, where the barometer was placed during the night, to be out of the way of any possible danger; and in the morning I commenced again. Among the powder horns in the camp, I found one which was very transparent, so that its contents could be almost as plainly seen as through glass. This I boiled and stretched on a piece of wood to the requisite diameter, and scraped it very thin, in order to increase to the utmost its transparency. I then secured it firmly in its place on the instrument with strong glue made from a buffalo, and filled it with mercury properly heated. A piece of skin, which had covered one of the vials, furnished a good pocket, which was well secured with strong thread and glue; and then the brass cover was screwed to its place. The instrument was left some time to dry; and, when I reversed it, a few hours after, I had the satisfaction to find it in perfect order, its indications being about the same as on the other side of the lake before it had been broken. Our success in this little incident diffused pleasure throughout the camp; and we immediately set about our preparations for ascending the mountains. As will be seen, on reference to a map, on this short mountain chain are the head-waters of four great rivers of the continent,--namely, the Colorado, Columbia, Missouri, and Platte Rivers. It had been my design, after having ascended the mountains, to continue our route on the western side of the range, and, crossing through a pass at the northwestern end of the chain, about thirty miles from our present camp, return along the eastern slope across the heads of the Yellowstone River, and join on the line to our station of August 7, immediately at the foot of the ridge. In this way, I should be enabled to include the whole chain and its numerous waters in my survey; but various considerations induced me, very reluctantly, to abandon this plan.