see the river, but they could not get down to it. E. L. Berthoud, the engineer, in 1861 also made an attempt, but gave it up after one day for the same reason. There was, indeed, only one way to fathom the secrets of this river, and that was to start above with good boats and go down on the tide; but as yet no man had appeared with sufficient nerve and good judgment to make a successful attempt at it. In 1861 Berthoud and Bridger explored a road from Denver to Salt Lake by way of Middle Park, crossing the Green near the mouth of the Uinta. This road was for the Overland Stage Company. Owing to the Civil War the project was abandoned, but a regiment of California volunteers marched this way from Salt Lake to Denver. The distance was 413 miles;[112] and there was small record of the features of the Wilderness through which the road ran. From the mouth of the Colorado at the Gulf of California up to within a short distance of Fort Yuma Lieutenant Derby, of the Topographical Engineers, made an examination in 1851, and later that same year George A. Johnson came to the mouth with supplies for Yuma, constructing there some flatboats for the purpose of transporting the cargo to the fort. The Gila at this time was the southern boundary in this quarter of the United States, but complications having arisen over an ill-defined portion of the line a new treaty was negotiated by Gadsden in 1853, by which, for a consideration of ten million dollars paid to Mexico, the boundary was placed where it is now. The mouth of the Colorado was not included, though navigation privileges were granted. The mouth of the river is of no value to Mexico and ought to be purchased by the United States, although the difficulty of navigation renders it of comparatively small importance. In order to arrive at the Yuma post, situated at the mouth of the Gila, a steamer adapted to this kind of navigation was brought by sea from San Francisco by Turnbull. This was to ply between the fort and the Gulf at the mouth of the Colorado. She was named _Uncle Sam_, and it was only a few months before she struck a snag and went to the bottom. The power of the river, the immense quantity of sediment brought down and shiftingly deposited by every slack current, the earthquakes, and the fierce tidal bore, rendered navigation anything but easy. Turnbull gave up, but Johnson took the contract for transporting the fort supplies from the Gulf and soon had a new steamer in service, the _General Jesup_. This was followed by a second, the _Colorado_, one hundred and twenty feet long. Johnson became familiar with every bar and current and for years continued skilfully to operate his boats. He knew the history of that locality as perhaps no other man could know it.[113] [Illustration: The Steamboat "Explorer" in which Lieutenant Ives, in 1858, Ascended the Colorado to the Foot of Black Canyon. Sketch by H. B. Mollhausen.]