From the mud volcano we moved up the valley about four miles to our camp on the river, passing several mud puffs on the way. One of the soldiers brought in a large string of river trout, but the water of the river is strongly impregnated with the overflow from springs near its bank, and is not palatable. Some of our party who have drank the water are feeling nauseated. Others think that their illness is caused by partaking too freely of one of the luxuries of our larder, canned peaches. I assuaged my thirst with the peaches, and have not partaken of the water, and there is no one in our camp in finer condition than I am. Lieutenant Doane's felon has caused him great suffering to-day, and I have appealed to him to allow me to lance it. I have for many years carried a lancet in my pocketbook, but I find that I have inadvertently left it at home. So all this day, while on horseback, I have been preparing for the surgical operation by sharpening my penknife on the leathern pommel of my saddle as I rode along. I have in my seamless sack a few simple medicines, including a vial of chloroform. Lieutenant Doane has almost agreed to let me open the felon, provided I put him to sleep with the chloroform; but I feel that I am too much of a novice in the business to administer it. However, I have told him that I would do so if he demanded it. Our elevation to-day is about 7,500 feet above sea level. Saturday, September 3.--This morning General Washburn and I left camp immediately after breakfast and returned four miles on our track of September 1st to Crater Hill and the mud springs, for the purpose of making farther examinations. We found the sulphur boiling spring to be full to overflowing, the water running down the inclined surface of the crust in two different directions. It was also boiling with greater force than it was when we first saw it, the water being occasionally thrown up to the height of ten feet. About 80 or 100 yards from this spring we found what we had not before discovered, a boiling spring of tartaric acid in solution, with deposits around the edge of the spring, of which we gathered a considerable quantity. In the basin where we had found so many mud springs we to-day found a hot boiling spring containing a substance of deep yellow color, the precise nature of which we could not readily ascertain. We accordingly brought away some of it in a bottle (as is our usual custom in such cases of uncertainty), and we will have an analysis of it made on our return home. In the same basin we also found some specimens of black lava.