7 8 4 THE POPULAR SCIENCE MONTHLY. 



dred feet in height. The last two rivers, entering the valley from the 

 east, cross it immediately and at once take a general northwest course. 

 The Grand flows on toward the northwest until it rounds the end of 

 the Uncompahgre Plateau, when it sweeps slowly around to the south- 

 west, and resumes its normal direction, still hugging closely the left 

 side of the valley. 



Southwest of the Uncompahgre Plateau the eye looks out over a 

 stretch of low, arid plateaus, traversed, in deep canons, by the Rio 

 Dolores and its tributaries. This stream is an important branch of the 

 Grand, entering it at the foot of the great valley, after that river has 

 passed around the end of the Uncompahgre Plateau, and just as it 

 plunges into the course of canons by which it passes the Sierra la Sal. 



Traveling along the crest-line of the Uncompahgre Plateau, one is 

 interested in observing how sharply the crest-line serves as a water- 

 parting. The drainage toward the west heads in the crest, without 

 cutting it at all. The bluff-wall is everywhere continuous. But in 

 the midst of these observations one is astonished by riding suddenly 

 to the verge of a tremendous gorge, thousands of feet in depth, which 

 apparently comes in from the west, and extends up into the plateau to 

 the northeastward, against the slope and dip of the strata, as far as 

 the eye can reach. Down in the depths he sees a small stream flow- 

 ing westward. Descending into this canon, an operation not easily 

 performed at any point, and traversing its bed northeastward, he comes 

 in a few miles to a divide in the canon, and beyond the divide he 

 finds a small stream flowing northeast into tbe Gunnison. This is the 

 Unaweep Canon. 



The Unaweep Caiion is cut across the Uncompahgre Plateau, from 

 the great valley of the Gunnison and Grand on the northeast, to the 

 low, desert plateaus on the southwest. Its course is nearly southwest, 

 and almost precisely at right-angles to the crest of the plateau. It 

 joins the Gunnison at a point about six miles above the mouth of the 

 latter stream, at an elevation above the sea of 4,600 feet. Tracing its 

 course south west ward, its bed is seen to rise slowly, but not so rapidly 

 as the level of the plateau, so that the caiion increases gradually in 

 depth. The bottom rises to a divide, 7,000 feet above sea-level, and 

 several miles east of the crest of the plateau. The walls at the divide 

 have a height of 1,200 feet. AVest of the divide, the slope of the bed 

 of the caiion changes slowly, and its descent to the westward does not 

 become very rapid until the crest of the plateau is passed. At the 

 crest, the height of the canon-walls is 3,000 feet. At the point of junc- 

 tion with the Rio Dolores, the elevation is 4,618 feet above the sea, or 

 practically the same as at its junction with the Gunnison. 



The first few miles from the Gunnison the canon is very narrow, 

 has no great depth, and is cut in soft, recent, sedimentary rocks. This 

 portion might easily have been cut by the small stream now occupying 

 it a theory which is supported by the fact that the strata here on 



