Military Ex])lorations and Surveys. 105 



ence to the line of travel, and, resting upon this rather imperfect 

 skeleton, the topography in sight of the line was sketched, while 

 that out of sight of the line was often added from the statements 

 of hunters, trappers and Indians. These lines were checked at 

 intervals by astronomic determinations, the latitude being deter- 

 mined by altitudes of the sun or a star, the longitude by moon 

 culminations or lunar distances, or by chronometer. 



Many such lines were run in various directions over the 

 Cordilleran region. " From such as were at that time available. 

 General G. K. Warren constructed in 1857 the first map of the 

 western United States which was in any way worthy of the name 

 of map. 



Nearly all of the areas thus explored have since been resur- 

 veyed by more accurate and detailed. methods. 



Survey of the 40th Parallel. — In 1867 Mr Clarence King, a civil- 

 ian in the employ of the War department, organized a survey 

 for the exploration of a strip of country adjacent to the line of the 

 Union Pacific and Central Pacific railroads, from the longitude 

 of Cheyenne on the east to the eastern boundary of California on 

 the west, and about 100 miles in breadth from north to south. 

 This work, which was completed in 1871, comprises an area of 

 about 87,000 square miles. It was published on a scale of 4 

 miles to 1 inch in approximate contour lines 300 feet apart. The 

 work was controlled by triangulation ; heights were measured by 

 barometer and by vertical angles, and sketching was done in 

 note books, the sketches being adjusted to the locations in the 

 office. 



Surveys tvest of the 100th Meridian. — This was the most exten- 

 sive of the surveys within the Cordilleran region. It was com- 

 menced in 1869, and for several years was carried on by traverse 

 methods similar to those followed by the other explorations 

 under the War department, and the maps produced were pub- 

 lished on a scale of 8 miles to an inch, the relief being expressed 

 by hachures. In 1873- '4-'5 the methods of this survey were 

 radically improved. A system of control by triangulation was 

 adopted, the scale of publication Avas increased from 8 to 4 

 miles to an inch, and areas, instead of lines of travel, were 

 mapped. This survey was discontinued in 1879. The entire 

 area surveyed is said to have been 361,000 square miles, of which 

 103,000 square miles was on a scale of 4 miles to an inch, the 

 balance being on that of 8 miles to an inch. 



