56 THE UNITED STATES GEOLOGICAL SURVEY. [bull. 227. 
Surveys may be divided into three classes: 
1. Those made for general purposes, or information surveys, which 
may be exploratory, geodetic, geographic, topographic, geologic, etc. 
2. Those made for jurisdictional purposes, or cadastral surve} 7 s, 
which define political boundaries and those of private property and 
determine the inclosed areas. 
3. Those made for construction purposes, or engineering surveys, 
on which are based estimates of the cost of public and private works, 
such as canals, railways, water supplies, etc., and their construction 
and improvement. 
The topographic survey, one of those in the first class, is made for 
military, industrial, and scientific purposes. The topographic map, 
made directly from nature by measurements and sketches on the 
ground, is the mother map from which all others are derived. It 
shows with accuracy all the drainage, relief, and cultural features 
which it is practicable to represent on the scale chosen. 
The act of March 3, 1879, which created the United States Geolog- 
ical Survey, appropriated $106,000 for a geologic survey and classi- 
fication of the lands of the public domain. The presentation of the 
results of a geologic survey- necessitates a good topographic map. 
There was in existence no such map of the greater part of the public 
domain; therefore, of the sum appropriated, $19,621: was allotted for 
topographic surveys during the first year. In 1882, after the change 
of directors from Clarence King to J. W. Powell, and the extension of 
the work to "the preparation of a geologic map of the United States," 
the topographic branch was reorganized by the appointment of a chief 
geographer, and the work was divided into the northeast, southeast, 
central, and western sections of topography. The allotment for topo- 
graphic surveys for the fiscal year 1882-83 amounted to $70,700, and 
necessitated a corresponding increase in the field force. 
A similar organization of the topographic branch was maintained, 
with slight changes, until the beginning of the fiscal year 1888-89. 
An act making appropriations for the fiscal year ending June 30, 1889, 
provided the sum of $199,000 for "topographic surveys in various 
portions of the United States." Thus, while during the first decade 
of the existence of the Survey topographic surveys were executed as a 
necessary adjunct to geologic work and the classification of lands, at 
the beginning of the second decade the value of the topographic maps 
for other purposes had become so apparent that Congress provided 
specially for their preparation and publication. 
During the first few years the present organization continued to 
use, in its map work, the same scale that had been employed by the 
earlier independent surveys — about 4 miles to the inch, or 1:250000, 
with relief shown by 200-foot contours; but when the cooperative 
surveys of the States were begun (see p. 60) it was seen to be desirable 
to increase the scale and contour interval, not only for the work in 
