FOKEWORD. 
Mineral resources are coming more and more into prominence as 
the basis upon which modern advance is built. Their adequate 
development is a matter of the first importance, and public opinion* 
will be called upon in increasing measure to shape the course of 
advance in this fundamental field. As the general subject i§ not 
one of popular experience, this series of papers is under preparation 
for the purpose of interpreting in nontechnical language the sig- 
nificant aspects of each resource of mineral origin, in anticipation 
of a growing demand for concise summations of technical knowledge 
in a form adapted to current use. 
The sources of energy underlie the employment of all raw mate- 
rial, and this paper on pow T er, together with those of this series on 
coal and petroleum, are designed to present a constructive analysis 
of the fuel situation in the United States. 
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