VI PREFA CE. and complete directions are given as to what should be done in case of emergency. The reasons for first explaining the construction and action and then asking and answering questions are three: first, when a question is asked and answered, and the reader does not thoroughly understand the construction and action of mechanism, the questions and answers will not be clear to him; second, the reader will be more vividly impressed by reviewing the questions and answers; third, the questions and an¬ swers are so arranged that the book can be used by Master Mechanics or Travelling Engineers for the ex¬ amination of candidates for promotion, or by the demonstrator in the Lodge Room. An effort has been made to present to the reader a full and clear explanation of the Compound Locomo¬ tive, showing the construction of different systems in actual use, and giving the method of disconnecting such engines when broken down. The author has illustrated the principal “ break¬ downs ” that happen to a locomotive, so that when one actually occurs on the road the engineer can com¬ pare the break with the illustrations in the book, and find out exactly what should be done. Each part of the mechanism is named in the illus¬ trations as a guide to the engineer in making out work reports. I am indebted to the proprietors of the works whose Compound Locomotives are shown in this book, for drawings and photographs; to the Westinghouse and New York Air-brake companies, and other manufactu¬ rers whose appliances have been illustrated and de-
