From whatever point of view considered, this expedition is one of the most remarkable in our annals. From Helena to the farthest point reached by the party, the route passed over was nearly three hundred miles long. The region of the Upper Yellowstone is perhaps the most difficult of access in the entire country. Even to-day, it is an almost certain place in which to get lost, if one is not thoroughly familiar with wilderness travel and happens to stray away from the beaten path. In 1870, moreover, the danger from hostile Indians was a constant and formidable menace, and the party was more than once reminded of it during the progress of the expedition. But in spite of all these difficulties, the success of the enterprise was so complete, its incidents were so full of romance, and its results were so far-reaching and important, that it well deserves the wide attention it has received. THE JOINT GOVERNMENT EXPEDITION OF 1871. The direct result of the expedition of 1870 was to cause the U. S. Geological Survey to change its programme for the season of 1871, so as to give attention to the new wonderland; and also to cause the military authorities to send a well-appointed engineer party to the same locality. These two expeditions, one under Dr. Hayden and the other under Captains Barlow and Heap, of the Engineer Corps of the Army, moved for the most part together, camping near each other, and accompanied by the same military escort. Particular attention will here be given only to such features of these expeditions as pertain to new discoveries. At the very outset of their journey, they branched off from the Washburn route at the mouth of the Gardiner River, and by ascending this stream, discovered the wonderful formations now known as the Mammoth Hot Springs. From this point, the parties traveled eastward to Tower Creek; thence over Mt. Washburn, and past the Cañon and Falls, to Sulphur Mountain, Mud Geyser, and the Lake; thence by a new route across the mountains to the Lower Geyser Basin; thence to the Upper Basin; thence east, across the mountains again, past Shoshone Lake to Yellowstone Lake; thence around the head of this body of water to its outlet; thence across the country, by separate routes, to the mouth of Soda Butte Creek; and thence down the East Fork to Baronett's Bridge (which had been built only a few months before), and out of the Park by way of Mammoth Hot Springs. The original work done by these parties, besides the discovery of the springs on the Gardiner, was the opening of a route between the Yellowstone River and the Lower Geyser Basin; the exploration of the Lower Basin; the mapping of the shore line of Yellowstone Lake, by Dr. Hayden; the mapping of the head waters of the Snake River, by Captain Barlow; and some hasty explorations in the valley of the East Fork of the Yellowstone, now called Lamar River.