CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1902. 
S. F. Emmons, 
C. W. Hayes, 
Geologists in Charge. 
INTRODUCTION. 
By C. W. Hayes, Geologist in Charge of Geology. 
This bulletin has been prepared primarily with a view to securing 
prompt publication of the economic results of investigations by the 
United States Geological Survey. It is designed to meet the wants of 
the busy man, and is so condensed that he will be able to obtain 
results and conclusions with a minimum expenditure of time and 
energy. It also affords a better idea of the work which the Survey as 
an organization is carrying on for the direct advancement of mining 
interests throughout the country than can readily be obtained from 
the more voluminous reports. Should this bulletin be favorably 
received by those interested in the development of the mineral indus- 
tries of the United States, it is proposed to publish early in each cal- 
endar year a similar bulletin containing the results of the last year's 
field work in economic geology. 
In the preparation of the present volume, promptness of publica- 
tion has been made secondary only to the economic utility of the 
material presented. The papers included are such only as have a 
direct economic bearing, all questions of purely scientific interest 
being excluded. 
The papers represent three classes: (1) Preliminary discussions of 
the results of extended economic investigations, which will later be 
published by the Survey in more detailed form; (2) comparatively 
detailed descriptions of occurrences of economic interest, noted by 
geologists of the Survey in the course of their field work, but not of 
sufficient importance to necessitate a later and more extended descrip- 
tion; (3) abstracts of certain economic papers which have appeared 
in Survey publications during the last year, chiefly such as give a 
general account of the distribution and mode of occurrence of 
particular mineral deposits throughout the United States. 
The papers have been grouped according to the subjects treated. 
At the end of each section is given a list of previous publications on 
that subject by this Survey. These lists will be found serviceable by 
those who wisli to ascertain what has been accomplished by the Sur- 
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