12 ALASKAN MINERAL RESOURCES IN 1906. 
distribution of the mineral deposits. It has been possible, however, 
to collect through correspondence considerable information in regard 
to the status of mining in the districts that were not visited by mem- 
bers of the Survey. The writer would here make acknowledgment to 
the many Federal officials, mine operators, and prospectors who have 
cooperated in the collection of these data. 
The statistics presented on later pages show that the value of the 
mineral production in Alaska still comes very largely from the placers. 
Therefore the description of placer districts — the most important 
source of the mineral wealth — predominates in this report as in pre- 
vious volumes. Again, as in previous years, a large part of the inves- 
tigations and surveys were directed to the mapping of the placer 
districts of the Yukon and Seward Peninsula, which are the largest 
producers. 
The composite authorship of this volume is evident from the fact 
that fifteen different papers are presented by eleven different authors. 
The arrangement of the contributions is, in general, geographic — from 
south to north. It is unfortunate that the exigencies of prompt pub- 
lication make it imperative to omit all elaborate illustrations, the 
reproduction of which necessarily consumes considerable time, and 
to include only such outline maps and diagrams as can be quickly 
prepared" for printing. 
PROGRESS OF SURVEYS. 
INTRODUCTION. 
In 1906 fourteen parties were engaged in field work during a period 
varying from two and a half to six months. The technical force of 
these parties included twelve geologists, four geologic assistants, four 
topographers, and two hydrographers, in addition to which about 
thirty camp men were employed. Eight of these parties carried on 
geologic investigations, two made topographic surveys, three com- 
bined both classes of work, and one was employed in stream measure- 
ments and hydrographic reconnaissance. The aggregate of the areas 
covered by geologic reconnaissance surveys during 1906 is 9,000 
square miles; by detailed geologic surveys, 548 square miles. Topo- 
graphic reconnaissance surveys were carried over an area of 10,768 
square miles; detailed topographic surveys, over an area of 40 square 
miles. Detailed hydrographic surveys were made over an area of 
200 square miles and reconnaissance surveys over an area of 1,000 
square miles. In addition to this, of the 28 Alaskan mining districts 
in which work is going on, 16, including all but one of the large pro- 
ducers, were visited by members of the Survey. The table on the 
next page presents a summary of the progress of surveys since the 
organization of systematic work in 1898. 
