F. GEOGRAPHY. 243 



tility, the labors of the Survey were confined to the comple- 

 tion of the Atlas of Colorado. Therefore the work of the 

 season of 1876 was devoted to finishing the entire mountain- 

 ous portion of Colorado, with a belt fifteen miles in width 

 of Northern New Mexico, and a belt twenty-five miles in 

 breadth of Eastern Utah. Six sheets of the Physical Atlas 

 are now nearly ready to be issued from the press. Each 

 sheet embraces an area of over 11,500 square miles, or a total 

 of 70,000 square miles. The maps are constructed on a scale 

 of four miles to one inch, with contours of 200 feet, which 

 will form the basis on which will be represented the geol- 

 ogy, etc. 



The point of departure the past season was Cheyenne, 

 Wyoming Territory. 



The primary Triangulation party was placed in charge of 

 A. D. Wilson, and took the field from Trinidad, the southern 

 terminus of the Denver and Rio Grande Rail way, August 18th, 

 making the first station on Fisher's Peak. From this point 

 the party marched by the valley of the Purgatoire, crossed 

 the Sangre de Christo Range by way of Costillia Pass, and 

 followed the west base of the range northward as far as Fort 

 Garland, making a station on Culebra Peak. About six 

 miles north of Fort Garland is located one of the highest and 

 most rugged mountain-peaks in the West, called Blanca Peak, 

 the principal summit of the Sierra Blanca group. On the 

 morning of August 28th the party started to ascend this 

 peak. They found no difficulty in riding to timber line, 

 which is here about 12,000 feet above sea-level. Here they 

 were compelled to leave the animals, and carry the instru- 

 ments themselves. The main summit is about two miles 

 north of the first point, in a straight line, and connected with 

 it by a very sharp ridge, difficult to pass on account of the 

 loose rocks and the constant fear of tumbling. After diffi- 

 cult climbing they found themselves on the summit. From 

 here a magnificent view was spread out before them. A 

 large portion of Colorado and Kew Mexico could be seen. 

 This point is the highest in the Sierra Blanca group, and, as 

 far as is known at the present time, is the highest in Colo- 

 rado. The elevation was determined by Mr. Wilson. First 

 a mean of eight barometric readings, taken synchronously 

 with those at Fort Garland, gave a difierence between the 



