382 HISTORY OF MECHANICS. 



edge a plurality of Mechanical principles ; and in the most recent 

 analytical treatises on the subject, all the doctrines are deduced from 

 the single Law of Inertia. Indeed, if we identify Forces with the Ve- 

 locities which produce them, and allow the Composition of Forces to 

 be' applicable to force so understood, it is easy to see that we can reduce 

 the Laws of Motion to the Principles of Statics ; and this conjunction, 

 though it may not be considered as philosophically just, is verbally 

 correct. If we thus multiply or extend the meanings of the term 

 Force, we make our elementary principles simpler and fewer than be- 

 fore ; and those persons, therefore, who are willing to assent to such a 

 use of words, can thus obtain an additional generalization of dynamical 

 principles ; and this, as I have stated, has been adopted in several re- 

 cent treatises. I shall not further discuss here how /ar this is a real 

 advance in science. 



Having thus rapidly gone through the history of Force and Attrac- 

 tion in the abstract, we return to the attempt to interpret the phenom- 

 ena of the universe by the aid of these abstractions thus established. 



But before we do so, we may make one remark on the history of 

 this part of science. In consequence of the vast career into which 

 the Doctrine of Motion has been drawn by the splendid problems pro- 

 posed to it by Astronomy, the origin and starting-point of Mechanics, 

 namely Machines, had almost been lost out of sight. Machines had 

 become the smallest part of Mechanics, as Land-measuring had become 

 the smallest part of Geometry. Yet the application of Mathematics to 

 the doctrine of Machines has led, at all periods of the Science, and es- 

 pecially in our own time, to curious and valuable results. Some of 

 these will be noticed in the Additions to this volume. 



