INSTRUCTION pertaining to Farm Machinery and Farm Motors has been quite recently added to the agricultural course in the majority of the agricultural colleges in the United States. Although the need and importance of such a study was self-evident, it was a new field, one in which the knowledge pertaining to the subject had not been prepared and systematized for instructional purposes. The latest book on the subject of Farm Machinery was written by J. J. Thomas in 1869, before the general introduction of labor-saving machinery for farm work. Many books have been written on the various motors used for agricultural purposes, but it is not believed that an attempt has been made to place in one volume a discussion of them all. The authors have felt the need of a text for instructional purposes, and it is this need that has prompted them to prepare this book. It is a revision of the lecture notes used before their classes for several years. These notes were prepared from a careful study of all the available literature on the subject, and from observation made in the field of the machines at work and in the factories where they are made.