The following books have been consulted and used in writing the Catechism of the Locomotive: Heat considered as a Mode of Motion, by Prof. Tyndall; The Conservation of Energy, by Balfour Stewart; Railway Machinery, by D. K. Clark; Treatise on the Locomotive Engine, by Zerah Colburn; Treatise on the Steam Engine, by W. J. M. Rankine; Indicator Experiments on Locomotives, by Professor Bauschinger; Richards’ Steam Indicator, by Charles T. Porter; Die Schule des Locomotivführers, by J. Brosius and R. Koch; Mechanics, by A. Morin; The New Chemistry, by J. P. Cooke, Jr.; Combustion of Coal and the Prevention of Smoke, by C. Wye Williams; A Treatise on Steam Boilers, by Robert Wilson; Reports of the American Railway Master Mechanics’ Association; Link Valve Motion, by William S. Auchincloss, and Emergencies and How to Treat Them, by Dr. Joseph W. Howe. For the title of the book an apology is perhaps needed, as the word Catechism is associated in nearly all persons’ minds we will trust with early religious and theological instruction, and therefore a Catechism of the Locomotive is very apt to sound more ludicrous than scientific. The title of Mr. Kosak’s book was adopted before it was determined to rewrite it, and it was afterwards not deemed best to change it. To those who are disposed to smile at it, the precedent of Mr. Bourne’s excellent Catechism of the Steam Engine is quoted, and if they will refer to Webster’s Dictionary for the definition of the word “catechism,” they will find that it means “an elementary book containing a summary of principles in any science or art, but appropriately in religion, reduced to the form of questions and answers, and sometimes with notes, explanations and reference to authorities,” which is exactly what the present book is intended to be. To persons accustomed to books and study, the catechetical form is very apt to seem cumbrous and awkward, but it has some very decided advantages in writing for those who have not acquired studious habits of thought. To such the question asked presents first a distinct image of the subject to be considered, so that the explanation or instruction which follows is much more apt to be understood than it would be if no such question had been asked. The author is indebted to Mr. D. B. Grant for the use of drawings from which most of the engravings of details of locomotives with which this book is illustrated have been made, and to other locomotive builders, whose engines are illustrated in the full-page plates, for the drawings thereof. He has also received very valuable aid from Mr. Richard H. Buel, Mechanical Engineer; Mr. William Buchanan, Master Mechanic of the Hudson River Railroad; Mr. Frank D. Child, Superintendent of the Hinkley Locomotive Works; and Mr. E. T. Jeffrey, Assistant Superintendent of Machinery of the Illinois Central Railroad.