The first edition of this book was published in 1913. It was new in its field and the experience since gained in teaching farm motors has led to the present revision. In this edition the chapters on gas and oil engines and on traction engines were enlarged, the steam engine chapters were rewritten and new chapters were added on automobiles and on animal motors. All other chapters were revised. In the preparation of this edition, the author is particularly indebted to President J. H. Waters and to his colleagues N. A. Crawford, W. A. Buck, E. V. Collins and F. A. Wirt of the Kan sas State Agricultural College. A, A, potter.