Excerpt from Interrelations of the Fossil Fuels When this study was taken up, the writer planned to present a synopsis of geological observations, then to summarize results oh tained from investigation of chemical relations of the fossil fuels and finally to discuss the problems involved. Illness, beginning in October, 1917, interrupted the study and no attempt to resume it was made until the summer of 1919. But the labor of reducing bulky abstracts to brief digests and of filling gaps in the accumu lated material became increasingly difficult, so that within a few months, it became certain that the work could not be completed by the writer, who, being well advanced in his 8oth year, could not hope that youthful vigor will return. He has prepared a table of contents and an index, which may render the portion, already published, more nearly available for those interested in the study. The War made communication with continental Europe very um certain during the time when preparation of abstracts of publica tions on Paleozoic coals were in course of preparation, so that there was little opportunity to consult Professors Barrois, Dannenberg Petrascheck, v. Ammon and other geologists, who had always been prompt in replying to my too numerous letters of inquiry, which must have tried their patience. My indebtedness to American geolo gists is very great; they have not hesitated to give me access even to unpublished material. It may seem invidious to make special men tion of any, but failure to recognize my obligations to Doctor David White and Professor Willis T. Lee would be inexcusable. I must make grateful acknowledgment of the unvarying and generous courtesy extended by Doctor I. Minis Hays, Secretary of the Amer ican Philosophical Society, and Professor R. A. F. Penrose, Jr., chairman of the publication committee. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.

This book gives an overview of the problem of providing economics with a biophysical foundation, explains the importance of energy in economic valuation and aims to develop novel ways of evaluating the physical constraints of our planet and the services provided by the natural environment.