This document is a reference for the enlisted men in the Navy whose duties require knowledge of the fundamentals of machinery. Beginning with the simplest of machines--the lever--the book proceeds with the discussion of block and tackle, wheel and axle, inclined plane, screw and gears. It explains the concepts of work and power, and differentiates between the terms "force" and "pressure." The fundamentals of hydrostatic and hydraulic mechanisms are discussed in detail. The final chapters include several examples of the combination of simple mechanisms to make complex machines. The text is illustrated throughout. (CSS)