FOREWORD. 
Mineral resources are coming more and more into prominence as 
the basis upon which modern advance is built. Their adequate de- 
velopment 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 is not one 
of popular experience, this series of papers is under preparation for 
the purpose of interpreting in nontechnical language the significant 
aspects of each resource of mineral origin, in anticipation of a grow- 
ing 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 petroleum, together with those on coal and 
power of this series, aim to present a constructive analysis of the 
fuel situation in the United States. 
