are also several works which contain collections of the mechanical contrivances which have been invented for the purpose of transmitting and modifying motion, and these works may be considered as treatises on the science of Pure Mechanism. But this science has not yet been reduced to the systematic simplicity which is desirable, nor indeed generally recognized as a separate science. It has been confounded, under the common name of _Mechanics_, with the other **science, Mechanics Proper, or Machinery, which considers the effect of _force_ transmitted by Mechanism from one part of a material combination to another. For example, the _Mechanical Powers_, as they are usually termed, (the Lever, the Wheel and Axle, the Inclined Plane, the Wedge, and the Screw,) have almost always been treated with reference to the relation between the _Power_ and the _Weight_, and not primarily as a mode of changing the velocity and kind of the motion. The science of pure motion has not generally been separated from the science of motion viewed with reference to its causes. [Note 15\2: _On a Method of expressing by Signs the action of Machinery._ _Phil. Trans._ 1826, p. 250.] Recently, indeed, the necessity of such a separation has been seen by those who have taken a philosophical view of science. Thus this necessity has been urged by M. Ampère, in his _Essai sur la Philosophie des Sciences_ (1834): 'Long,' he says, (p. 50,) 'before I employed myself upon the present work, I had remarked that it is usual to omit, in the beginning of all books treating of sciences which regard motion and force, certain considerations which, duly developed, must constitute a special science: of which science certain parts have been treated of, either in memoirs or in special works; such, for example, as that of Carnot upon Motion considered Geometrically, and the essay of Lanz and Betancourt upon the Composition of Machines.' He then proceeds to describe this science nearly as we have {158} done, and proposes to term it _Kinematics_ (_Cinématique_), from κίνημα, motion.