No one could deny these weird tales.

No one knew.
But Powell was fortified by Science, and he surmised that nowhere would he encounter any obstruction which his ingenuity could not surmount.
I remember one morning, on the second voyage, when we had made an early start and the night-gloom still lingered in the depths of Marble Canyon as we bore down on a particularly narrow place where the river turned a sharp bend to disappear between walls vertical at the water, into a deep-blue haze, it seemed to me that ANYTHING might be found there, and looking up from my seat in the bow of our boat into the gallant explorer's face, I said: "Major, what would you have done on the first trip if just beyond that bend you had come upon a fall like Niagara ?" He regarded me a moment with his penetrating gaze, and then answered: "I don't know." Perhaps he thought that what we now would find there was enough for the moment.
Captain Mansfield, reporting to the Secretary of War, wrote in his letter of December 10, 1867: "Above Callville for several hundred miles the river is entirely unknown." He recommended Callville as the starting-place for exploration, and a small steamer for the work, with skiffs and canvass boats for continuing beyond the steam-navigation limit; but Captain Rodgers, who had gone with the steamboat Esmeralda up through Black Canyon, thought the great canyon should be entered above Callville after the fall of water in the spring, and his was more nearly a correct idea.

The War Department continued, however, to butt against the wrong end, even after the success of the other way had been demonstrated.

Some Mormons, who did not know, reported the two hundred miles above Callville to be better than the one hundred below.

The two hundred miles above contain some of the most dangerous portions of the river.