334 



GEOGRAPHICAL PROGRESS AND DISCOVERY IN 1876. 



triangulation party, tinder the direction of A. 

 D. Wilson, started from Trinidad on the 18th 

 of August, and made its first station on Fish- 

 er's Peak. Thence they passed through the 

 valley of the Purgatoire, and across the Sangre 

 da Cristo range over the Gostilla pass, and 

 skirted the range northward as far as Fort 

 Garland, making another station on Culebra 

 Peak. About six miles north of Fort Garland 

 they explored one of the highest and most 

 difficult summits of the Rocky Mountains, 

 Blanca Peak, the highest point in the Sierra 

 Blanca group. They reached the timber-line, 

 12,000 feet above the ocean, without difficulty, 

 and, leaving their animals here, picked their 

 way up the crumbling, rocky slope to a pro- 

 jecting point only 600 feet lower than the 

 chief summit, and two miles distant. From 

 this they made their way along an arduous and 

 dangerous zigzag ridge to the base of the sum- 

 mit, which they soon mounted. This point is 

 the highest in Colorado as far as is yet known, 

 and the view from it embraces the greater 

 portion of Colorado and New Mexico. Its ele- 

 vation was determined by barometric readings, 

 the mean of eight being taken, compared with 

 synchronous readings made at Fort Garland : 

 a verification by trigonometry from the angles 

 of elevation and depression, fore and back, 

 showed a discrepancy of only two feet. The 

 elevation is 14,464 feet (Mount Harvard is 

 14,384 feet above the sea-level ; Gray's Peak, 

 14,341 feet ; Mount Lincoln, 14,296 feet; Mount 

 Wilson, 14,280 feet; Long's Peak, 14,271 feet; 

 Uncompahgre Peak, 14,236 feet; Pike's Peak, 

 14,146 feet; there are as many as fifty peaks 

 in Colorado exceeding 14,000 feet in elevation). 

 From here the party advanced westward across 

 the San Luis Valley, and followed np the Rio 

 Grande to its source, making a station near 

 the mountain-summits and another on the Rio 

 Grande Pyramid. Leaving the source of the 

 Rio Grande, they crossed the Great Divide, 

 and, passing through the Animas Park by trail, 

 reached Parrott City. They made a primary 

 station on La Plata Peak, and, crossing the ir- 

 regular table-lands west of the Dolores, com- 

 pleted a survey which they had not finished the 

 S3ason before on account of the hostilities of the 

 Ute Indians. They made a station on the high- 

 est of the Abajo Mountains, and then turned 

 their course eastward, making a station on Lone 

 Cone, and, crossing the Grand and Gnnnison 

 Rivers, reached the volcanic table-land at the 

 source of White River. The Wilson party 

 mapped out 1,000 square miles of territory dur- 

 ing the season, and established eleven primary 

 positions, covering by primary triangles all of 

 Southern and Western Colorado. Accompany- 

 ing the triangulation party, Mr. Holmes made 

 a geological journey which took in Colorado 

 and portions of Utah and New Mexico, obtain- 

 ing a general survey of the great plain-belts 

 oa both sides of the chain of the Rocky Moun- 

 tains; he observed a remarkable uniformity 

 in the disposition of the strata everywhere, 



there being scarcely an interruption in the 

 cretaceous formation, particularly, from the 

 northern part of New Mexico to Southwest 

 Wyoming. In one group of rooks, however, 

 there is a remarkable disparity between the 

 outcrops on the eastern and western sides of 

 the divide : the upper cretaceous rocks, includ- 

 ing numbers four find five, on the west side, 

 comprise over 2,000 feet of coal-bearing stra- 

 ta, chiefly sandstone, forming the tops of the 

 Mesa Verde and Dolores plateaus, and in the 

 Grand River Valley, where it forms the enor- 

 mous Hogback, attaining a thickness of 3,500 

 feet; but on the eastern side this group of 

 rocks is only represented by a few hundred 

 feet of shale and laminated sandstone. The 

 Abajo group Mr. Holmes found to consist of 

 trachyte, which had been forced up through 

 fissures in the stratified rocks, like the four 

 other isolated groups in the same region. He 

 places the northern limit of the cliff-habita- 

 tions of Colorado and Eastern Utah at not 

 above 37 45' north latitude. The Grand River 

 division was directed by Henry Gannett, as 

 topographer, accompanied by A. C. Peale, ge- 

 ologist, and by James Stevenson, the general 

 manager of the survey, who went along to 

 deal with the Indians, fearing that they might 

 again disturb the survey as they did last year. 

 Their first task for this season was to survey 

 about 1,000 square miles, lying mostly north 

 of the Grand River and south of the parallel 

 39 30' north, and between the meridians 108 

 and 109 30' west. They reached the field 

 from Cafion City about the middle of August, 

 and, going to the district south of the Sierra la 

 Sal, after securing the services of several In- 

 dians at the Ute agency of Uncompahgre, they 

 completed the survey of this country, which 

 is an irregular plateau with some curious feat- 

 nres, in eleven days. The Grand River, be- 

 tween the debouchures of the Gunnison and 

 Dolores, flows through a valley of twelve miles 

 average breadth, which was skirted on one 

 side by the perpendicular cliffs, called the 

 Roan or Book cliffs, rising in a succession of 

 terraces to a height of 4,000 feet, and forming 

 the termination of a broad plateau ; the course 

 of the river here is northwest for twenty-five 

 miles, then southwest, and then south for about 

 seventy-five miles. This plateau, which de- 

 clines very gradually on the other side to the 

 north-northeast, extends from the Wahsatch 

 Mountains on the west to the lower elevations 

 of the Park range on the east, and is cut 

 through by the Green River, which flows in th* 

 contrary direction to the dip. South of the 

 plateau are broken cliffs, and to the north of 

 it is the White Cafion. After leaving the Un- 

 compahgre agency the party went over to the 

 Grand River, following it down to the Dolores, 

 latitude 38 50' north, longitude 109 17' west, 

 From there they passed northward to the top 

 of the Book Plateau, following the crest east- 

 ward for 100 miles, and then descended to the 

 Grand and followed its course up to longitude 



