This work has been prepared in an attempt to satisfy the demand for a handy volume on coal. There already exists a very valuable literature on this important subject, but it is so voluminous and scattered that much of it is not accessible to the average reader. Many of our older works need revision because of new discoveries in the study of coal, such, for example, as the practical application of the microscope in the determination of its physical character and the discovery of more refined chemical processes for determining its chemical properties. The great advances in extracting coal from the earth by mechanical means and in the cleaning and coking of the products of the mine also make it necessary to bring new processes to the attention of the public.<br><br>There are so many different phases in the discussion of a subject so broad as this that details regarding many matters must be omitted in a one-volume work, and readers desiring detailed descriptions of machines or complicated processes must consult works dealing with those matters alone. While many topics are fully dealt with in this text, such as the properties, the origin, the uses and the general distribution of coal, some others as mining machinery, and details of distribution and character of local coal deposits can be treated only in works of several volumes. It is hoped, however, that the data presented will serve, for ready reference, those who make frequent use of a work of this type.<br><br>I wish to take this opportunity of expressing my appreciation to those who have so generously contributed to this work. My thanks are specially due to Dr. H. Ries of Cornell University, at whose suggestion the preparation of this text was undertaken, for suggestions and the use of photographs and cuts.