This book and its companion volume for the wood-working trades, first cover the general principles of science common to all industry, this material Being identical in the two books. Additional material follows this, that relating specifically to the metal trades appearing in this volume, and that relating particularly to the wood-working trades appearing in "Applied Science for Wood-Workers." The books are constructed in this way to meet the needs of particular industrial, trade, continuation, or apprentice classes where the instruction is intensive.

Every craftsman should not only be trained in the handicraft of his trade, but, if he is to be a really skilled worker, should also master the scientific principles involved; that is, he should become familiar with the reasons underlying the various operations which he performs. Such knowledge is obtained through the study of industrial science. The teaching of related trade knowledge is not, so far as the author knows, adequately covered in any system of industrial education.

Experience proves that, though the average pupil who completes the regular high school course may know the principles of the sciences in an abstract way, he is unable to recognize these principles in operation in the every-day work of the world. This fact is not surprising. Observation shows that many minds are able to grasp a principle in the abstract but are not able readily to apply that principle in practice.

Therefore, the study of the application of the scientific principles underlying modern industry is worthy to be treated as a special subject.

The author believes that there is a place for the traditional courses in chemistry, physics, and biology in the regular high school, in addition to the first-year science course. He also believes that there is a type of mind in our intermediate and secondary schools that can profit by the study of the principles of science underlying the fundamental trades. A course of this kind should develop in a boy's mind that attitude of alertness toward theory on which all sound practice is based - a mental attitude which will be valuable to all manual workers, and particularly to those who are to enter the distributive or productive spheres of industry. Hence the title of this book, "Applied Science for Metal-Workers," the purpose of which is to provide an elementary course in applied science for the metal trades.

The author wishes to express his thanks to the following firms who have kindly furnished cuts and information: Dodge Sales and Engineering Company, The Lincoln Electric Company, The American Injector Company, Brown and Sharpe Manufacturing Company, Tolhurst Machine Works, Buffalo Forge Company, Bailey Meter Company, Novo Engine Company, Nicholson File Company, The Bigelow Company, Ingersoll-Rand Company, Babcock and Wilcox Company, American Steam Gauge and Valve Manufacturing Company, The L. S. Starrett Company, Norton Company, Millers Falls Company, James B. Clow and Sons, Watson Stillman Company, American Radiator Company, Whitall Tatum Company, Youngstown Sheet and Tube Company, Eber-hard Faber, David Williams Company, American Screw Company, Enterprise Manufacturing Company, Edison Storage Battery Company, Independent Pneumatic Tool Company, Riehle Brothers, National Carbon Company, Inc., Worthington Pump and Machinery Company, Western Electric Company, Greenfield Tap and Die Corporation.

Acknowledgment is also made of indebtedness to the teachers who have kindly read the manuscript and offered valuable suggestions.

The author will be pleased to receive any constructive criticism of the book.

William H. Dooley.

New York City, August 15, 1919.