106 Henry Gannett — Mother Maps of the United States. 



The Hayden Survey. — This organization, which was initially a 

 geologic exploration, was instituted in 1867. No topographic 

 work was done by it until 1871, when certain route surveys were 

 made in Montana, Idaho and Yellowstone park. In 1872 similar 

 suryeys were carried on in the same region. Between 1873 and 

 1876, inclusive, the work of this organization was confined to 

 Colorado and adjacent strips of Arizona, New Mexico and Utah, 

 while in 1877 and 1878 work was done in Wyoming, Idaho, Utah 

 and YelloAvstone park. During 1873 and following years the 

 methods of survey were greatly improved. The work was con- 

 trolled b}^ triangulation originating in measured bases, within 

 which was -a secondary triangulation, by means of which nearly 

 all control points were located ; traverse being used to locate only 

 minor details of roads, streams, etc. Sketching was done in note 

 books, and the .sketching was adjusted to the control in the office. 

 The maps were published on a scale of 4 miles to an inch, in 

 approximate contour lines 200 feet apart. Altogether an area of 

 about 100,000 square miles was surveyed by this organization, 

 which was discontinued in 1879. 



Poivell Survey. — This survey originated in an exploration of the 

 Colorado river, commenced in 1867. After the completion of this 

 exploration, systematic Avork was undertaken in the territory of 

 Utah, and up to the time of the discontinuance of the survey in 

 1879 about 67,000 square miles had been surveyed, comprised in 

 Utah and the northern part of Arizona. The methods of work 

 were quite similar to those of the Hay den. survey, but with this 

 notable exception, that the minor control and the sketching were 

 done upon planetables, the sketching being adjusted to the con- 

 trol in the field upon the stations. The maps were published 

 by the present Geological survey on a scale of 1 : 250,000, the 

 relief being expressed by contours 250 feet apart. 



Boundary Surveys. — The boundary lines of many of the western 

 states and territories have been run at the expense of the general 

 government, and in connection with these boundary surveys 

 narrow strips of topography have been mapped. 



In 1875, when public attention had become drawn to the gold 

 deposits of the Black hills, an exploration of this region was 

 undertaken by the Indian bureau under the authority of the 

 general government. This exploration included both the prep- 

 aration of a topographic map and a geologic examination. The 



