This kenyon terminates thirty [should be three hundred] miles above the gulf.

To this point the river is navigable.

The country on each side of its whole course is a rolling desert of loose brown earth, on which the rains and the dews never fall.
A few years since, two Catholic missionaries and their servants on their way from the mountains to California, attempted to descend the Colorado.
They have never been seen since the morning they commenced their fatal undertaking.
"A party of trappers and others made a strong boat and manned it well with the determination of floating down the river to take beaver that they supposed lived along its banks.

But they found themselves in such danger after entering the kenyon that with might and main they thrust their trembling boat ashore and succeeded in leaping upon the crags and lightening it before it was swallowed in the dashing torrent." They had a difficult time in getting out of the canyon, but finally, by means of ropes and by digging steps with their rifle barrels, they reached the open country and made their way back to the starting-point.
This was, possibly, the expedition which was wrecked in Lodore, after Ashley's Red Canyon trip.

I have not succeeded in finding any other account that would fit that place.