On Eccentric and Centric Force: A New Theory of Projection is a book written by Henry F. A. Pratt in 1862. The book is a theoretical treatise on the principles of projection, which is the process of creating a two-dimensional image of a three-dimensional object. Pratt's theory proposes that there are two types of force at work in the projection process: eccentric force and centric force. Eccentric force is the force that acts upon the object being...