Though the canyons of the Colorado had now been crossed midway of the great six-hundred-mile stretch, and farther north near Green River Valley had far back in the century been penetrated to a limited extent, almost nothing was actually known about them. Even at the most favourable points approach to the brink was extremely difficult, and descent to the water generally impossible. On each side the country was for many miles forbidding wilderness, for the journeys of the trappers, where they had penetrated, had left no impression. It was as if no white man had ever looked upon it. They were thus the final great problem of the Wilderness. A stout heart was required to launch forth into their unfathomed mystery, particularly as by this time numerous tales of underground channels, fearful cataracts, and chasms impossible of passage, went the rounds of the camp-fires. For a time the Civil War withdrew attention from Western exploration, but when it was ended one of the officers, who had gone through the weary four years, and who wore in consequence an armless right sleeve, turned his attention once more to his scientific studies, and finally found himself, in 1867, exploring in the Parks of Colorado. Here he learned of the wonderful and forbidding canyons of the great river, saw some of the minor tributary gorges, and also met and employed a rare mountaineer, Jack Sumner, also a veteran of the Civil War. Sumner says he suggested to Powell the descent of the canyons. At any rate, Powell became enthused with a desire to explore this remnant of the original Wilderness, and Sumner was a more than willing companion in the scheme. Organising an expedition Powell started from Green River Station, Wyoming, in the same valley where the early trappers had so often made their rendezvous, and which had also been the resting-place for the California pioneers. He was a geologist and his experienced eye and quick judgment doubtless soon disclosed to him the probable nature of the interior of the canyons; the probability that no insurmountable obstacle existed to prevent his triumphant descent through the whole series. But while he believed the canyon mystery could be solved he went at it with no spirit of bravado. With him it was serious, scientific business, solely for the purpose of determining the geologic and geographic character of the mighty gorges in which the river lost itself. As the difference between the altitude of Green River Station and that of the mouth of the Rio Virgin was known to be some five thousand feet, there was clearly room for realisation of all the fantastic tales of the mountaineers. [Illustration: Running the Colorado. Drawing by F. S. Dellenbaugh.]