KINETIC OK MECHANICAL VIEW OF NATURE. 5 



the name of the kinetic ^ theory or view oi uaiuie. 

 It has frequently been phiced in opposition to the atomic 

 theory, and the history of the natural philosophy of the 

 earlier ages, down to Newton, has in recent years been 

 written from this point of view.^ If everything is 

 motion, there must still be something that moves, and 

 the question arises, What is it that moves ? The 

 system of Epicurus, and the great poem in which it has 

 found a classical expression, are really more occupied with 

 describing the final elements of matter — the so-called 

 nature of things — than with studying the different modes 

 of their motion. In the atomic theory, in the conception 

 of an infinite number of moving particles, the kinetic 

 tendency of thought repeatedly found botli in auricnt 



" There is no certainty in science 

 ■where some mathematics are not 

 appHcable "' (quoted by Lasswitz, 

 ' Geschichte der Atomistik,' 1890, 

 vol. ii. p. 11) ; and Leibniz, in a 

 letter to Foucher dated 1693, con- 

 demns his earlier tract entitled 

 ' Hypothesis Physica ' as a ''juvenile 

 attempt of one who had not yet 

 fathomed mathematics " (Ger- 

 hardt's edition of Leibniz's ' Philo- 

 so])hische Schriften,' vol. i. p. 415). 

 1 The word " kinetic " seems to 

 have been introduced into scientific- 

 literature Ijy Ampere, who uses the 

 term " cin(5mati([ue " to denote that 

 portion of mechanics where ' ' les 

 mouvements sont considores en eux- 

 memes, tels que nous les observons 

 dans les corps qui nous environ - 

 nent, et sjiecialement dans les 

 appareils appek's machines " ( ' Essai 

 sur la Philosojihie des Sciences,' 

 1834). In English text-books the 

 term kinematics, following Thom- 

 son and Tait ( ' Natural Philnsophy,' 

 Preface), is used to dcuDte what 

 PVench writers call " cincmatique 



pure," formerly called "phoro- 

 nomie," the doctrine of the purely 

 geometrical properties of motion, 

 without reference to the cause of 

 motion ; the consideration of the 

 latter being the special study of 

 "kinetics," which, together with 

 " statics," is comprised in the term 

 "dynamics." The acceptance of 

 the word " kinetic " to denote the 

 view that motion is at the bottom 

 of all natural jirocesses dates prob- 

 ably from the writings of Thomson 

 (Lord Kelvin), Tait, and Clerk 

 Maxwell, who, under the influence 

 of Newton and the great French 

 school of Lagrange, Ampere, Poin- 

 sot, Poncelet, and others, have re- 

 formed English, and subse<iuently 

 also German, thought and nomen- 

 clature in these subject-s. 



- I refer to the highly interesting 

 and important work of Professor 

 Kurd Liisswiti!, ' (Jcschichte der 

 Atomistik vnm ^littelalter bis 

 Newton,' 2 vols., Hamburg and 

 Leipzig, 1890. 



