XVI EEPOKT UNITED STATES GEOLOGICAL SURVEY. 



ing in the management of the Indians, who last year prevented the com- 

 pletion of the work in their locality by their hostility. 



The work assigned this division consisted in part of a small area, con- 

 taining about 1,000 square miles, lying south of the Sierra la Sal. The 

 greater portion of the work of this division lay north of the Grand Eiver, 

 limited on the north by the parallel of 39° 30', and included between the 

 meridian of 108° and 109o 30'. 



This division took the field at Caiiou City, Colo., about the middle of 

 August. The party traveled nearly west up the Arkansas River, over 

 Marshall's Pass and down the Tomichi and Gunnison Elvers to the Un- 

 compahgre (Ute) Indian agency. Here they secured the services of sev- 

 eral Indians as escort in the somewhat dangerous country which they 

 were tirst to survey. This area, lying south of Sierra la Sal, was worked 

 without difficulty. It is a broken plateau country, and presents many 

 extremely curious pieces of topography. Eleven days were occupied in 

 this work. 



The Grand Eiver, from the moutb of the Gunnison Eiver to that of the 

 Dolores, i 6., for nearly 100 miles, flows along the southern edge of a 

 broad valley, much of the way being in a low caiion, 100 to 200 feet deep. 

 The course of the river is first northwest for 25 miles ; then, turning 

 abruptly, it flows southwest, and then south, for about 75 miles. This 

 valley has an average width of 12 miles. It is limited on the north and 

 west by the "Eoan or Book Cliffs," and their foot-hills, which follow the 

 general course of the river. These cliffs rise from the valley in a suc- 

 cession of steps to a height of about 4,000 feet above it, or 8,000 to 8.500 

 feet above the sea. 



From its crest this plateau (for the Book Cliffs are hut the southern 

 escarpment of a plateau) slopes to the north-northeast at an angle of not 

 more than five degrees. It extends from the Wahsatch Mountains on 

 the west to the foot-hills of the Park range on the east, and presents 

 everywhere the same characteristics. The Green Eiver crosses it, flow- 

 ing in a direction exactly the reverse of the dip. It borders the Grand 

 on the north for 100 miles, the crest forming the divide between the 

 Grand and the White. On the south side of the crest are broken cliffs ; 

 on the north side, the branches of the "White canon immediately. This 

 leaves the divide in many places very narrow, in some cases not more 

 than 30 to 40 feet wide, with a vertical descent on the south toward the 

 Grand Eiver, and an extremely steep earth-slope (35° in many cases) at 

 the heads of the streams flowing north to the White Eiver. This crest, 

 though not over 8,500 feet in height, is the highest land for a long dis- 

 lance in every direction. 



After leaving the Uncompahgre agency, the party followed Gunni- 

 son's Salt Lake road to the Grand and down that river to the mouth of 

 the Dolores, in latitude 38° 50', longitude 109° 17'. At this point they 

 turned northward, and went up to the crest of the Book plateau. They 

 followed the crest to the eastward for upward of 100 miles, or to longi- 



