44 THE UNITED STATES GEOLOGICAL SURVEY. [bull. 227. 
work of the Geological Survey. The topographic maps arc the graphic 
expression of these geographic facts, undone of the most important func- 
tions of the Survey in Alaska has been the production of such maps. 
Most of the expeditions have had at least one topographer, and from 
even^ expedition a map of the route traversed has resulted. The value of 
these maps can not be overestimated. There are demands for them 
from prospectors, engineers, capitalists, and school-teachers, and they 
form one of the most essential preliminaries toward the development 
of the country in any direction. They indicate routes of travel to the 
prospector and explorer, railway and wagon routes to the locating 
engineer, and possible sources of water power to the mine operator. 
An area of from 90,000 to 100,000 square miles — about one-sixth of 
the total area of Alaska — has been covered by topographic surveys. 
The results have been compiled on a map which will be included in a 
forthcoming report designed to give a comprehensive account of the 
geography of the Territory. 
In connection with the Alaskan work, the explorers have used many 
new names for streams, mountains, and the other features discovered. 
In the office these names have been collected and brought into the 
form of a geographic dictionary of Alaska, which gives the locations 
of the features named, in many cases the origin and meaning of the 
name, and a chronologic list of authorities. 
While the aim of the work has been to investigate the mineral 
resources, this necessitated geologic studies, for it is only on a basis of 
thorough geologic knowledge that the facts gathered in regard to the 
value and distribution of ore deposits can be adequately interpreted. 
From year to year this fundamental knowledge is growing, and in 
course of time the geologic history of the Territory will be deciphered. 
Much is already known of the general succession and distribution of 
the bed-rock formations, and in a few years it will be possible to 
publish a preliminary geologic map. 
The studies of the bed-rock geology, extended by each expedition, 
are resulting in an accumulation of material which becomes increas- 
ingly valuable in tracing the distribution and origin of deposits having 
economic value. The occurrence of such deposits is but a minor 
feature of the general geology, but the most important factor in the 
development of the country. The function of the Survey is to study 
the relation of the two, and in the course of these studies results of 
immediate practical importance to the people of Alaska have been 
achieved. These have been chiefly in connection with the occurrence 
of gold, copper, tin, and coal. 
In 1895 and 1896 the gold-bearing localities of the southern coast 
were visited and facts of ecomomic value were collected regarding the 
occurrence of the gold and its relation to the country rock. Investi- 
gations were made of the mining districts along the Yukon River, 
