"mining all within ' 225 



lengthy quotations. Soine of these references are in the ex- 

 tended comments to the chapters on light, but by no means all. 



Encouraged in his criticisms by this new ammunition, Clarke 

 now carries the war into the enemy's camp. His earlier dis- 

 cussion of the application of gravity to the motion of planets 

 is now preceded by four arguments showing that " the vortices 

 of matter in which the planets swim, are mere fictions and 

 contrary to the phenomena of nature." ^^ Rohault's paragraph 

 headed " that these three elements are not imaginary," pre- 

 viously allowed to pass, now has a note beginning " these three 

 elements are to be looked upon as fictitious and imaginary." ^^ 

 The Cartesian subtle matter is now a " fiction . . . very weak, 

 and contrary both to reason and experience." *" At last Clarke's 

 notes begin to provide a systematic refutation of the text. 



At the same time the positive teaching in the notes is greatly 

 increased. Perhaps nothing illustrates their role in this respect 

 better than the inclusion of " six whole dissertations " by 

 Charles Morgan, a contemporary of Clarke at Cambridge and 

 later Master of Clare College. These were important enough 

 to merit republication as a separate tract in 1770, long after 

 the Cartesian controversy had been settled in Newton's favor. 

 Three of the dissertations, on the motion of falling bodies, on 

 the motion of projectiles, and on the descent of bodies falling 

 in a cycloid, together form a single footnote occupying over 

 a dozen pages of small print and ostensibly provoked by 

 Rohault's innocuous remark that falling bodies accelerate.*^ 

 Clarke clearly feels that he must take opportunities of com- 

 plementing the text over and above what is strictly necessary 

 to the establishment of Newtonian philosophy.*" 



One particularly interesting note contains Clarke's doctrine 



="'?. 311. 



'' P. 105, my italics. 



*"?. 25. 



*^ The acknowledgement to Morgan is made in the Translator's Preface. Clarke's 

 presentation copy to Morgan is in the possession of Clare College, Cambridge. 



*^ Mouy (op. cit., p. 137) erroneously supposes these dissertations to be by 

 Clarke and to be " ses critiques principales." 



