728 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



Azimuths and distances from Leon Pealc to — 



Names. 



Azimuths. Distances 



Mount Wilson 



Lone Cone 



Monnt Peale 



North Mam Peak . . . 



Sopris Peak 



West Elk Peak 



Uncompabo-re Peak . 

 Mount Sueffels 



Azimuths and distances from North Mam Peak to — 



Names. 



Monnt Peale 



Mount Powell 



Mountain of the Holy Cross 



Sopris Peak 



Snow-mass Mountain 



West Elk Peak 



Uncornpabgre Peak 



Leon Peak 



Chapter II. 

 METHODS OF TOPOGEAPHICAL FIELD AND OFFICE WOEK. 



The secondary triangulatioa was carried on by the topographers, in 

 connection with the topographical work, with small theodolites reading 

 to minutes of arc, and carrying a jjowerful telescope; these secondary 

 triangles summed up with a mean error of closure of about two minutes. 

 But as this work was constantly checked by the primary points, the 

 errors could not accumulate sufiQcient to be perceptible on the maps. 



The topographical field-work was carried on in the following man- 

 ner : — 



First, the region of country to be surveyed would be divided as nearly 

 as possible by natural boundaries into areas sufficiently large to employ 

 a party the whole season. 



Before taking the field, the topographer supplies bimself with all 

 the information possible as to character of country, &c., and collects all 

 the old maps that might give any idea of the existing trails, roads, or 

 places where supplies may be obtained. Each field-party is composed 

 of a topographer, geologist, assistant topographer, and sometimes a 

 botanist or zoologist would accompany the party ; these, with a cook, 

 and two or three packers, would complete the party. The geologist and 



