On the fourth day in Cataract Canyon three portages were compulsory at the very outset to pass safely over a stretch where the waters tumbled seventy-five feet in three quarters of a mile, and at the end of this three quarters of a mile they camped again, worn out by the severe toil.  Rapids now came with even greater frequency, between walls more than two thousand feet high and often nearly vertical from the water.  On the 27th a flock of mountain sheep was discovered on the rocks not more than one hundred feet above their heads.  The game did not see the hunters, who landed quickly in a convenient cove, and two fat sheep were added to the rapidly diminishing larder.  On the next day they were startled by the sudden closing in of the walls, till the canyon, now nearly three thousand feet deep, became very narrow, with the river filling the chasm from one blank cliff to the other.  The water was also swift and the canyon winding, so that it was not possible to see ahead.  Powell was much disturbed lest they should run upon some impassable fall, but luckily in about a mile and a half they emerged again into a more broken gorge without having had the least difficulty.  He justly remarks that after it was done it seemed a simple thing to run through such a place, but the first doing of it was fraught with keen anxiety.  In the late afternoon of this same day, they came to the end of the forty-one miles of Cataract Canyon, marked by a deep canyon-valley entering from the left at a sharp bend where millions of crags, pinnacles, and towers studded the summit of the right-hand wall, now again thirteen hundred feet high.  It was called Millecrag Bend, either then, or on the second expedition.  A new canyon immediately formed; a narrow, straight canyon, with walls terraced above and vertical below.  The thirteen hundred feet of altitude speedily diminished and in nine miles the voyagers were at the end.  Low walls again began, forming the head of the next canyon of the series.  Presently they arrived at the mouth of a river flowing in from the right, or west.  The pilot boat ran up into this stream, and as the water of the Colorado had been particularly muddy, the men were eager to discover clear, sparkling affluents and springs.  One behind shouted, “How is she, Jack?” and Jack sententiously replied, “Oh, she’s a dirty devil!” and by this title the river was long called, and probably is still so known in that region, though on the maps it was afterwards changed by Powell to Fremont River, in honour of the Pathfinder.

They were now in the beginning of what has since been called Glen Canyon.  Powell at first gave the name of Mound to the upper half, and Monument to the lower, but after 1871 Glen was substituted for the whole.  On July 31st they passed the mouth of the San Juan, which enters through a canyon similar to that of the main river, about a thousand feet deep.  They tried to climb out near this point, but failed to accomplish it.  The next day they made camp