i9l Comets : Reception of the Prindpia 239 



the tail is formed by a stream of finely divided matter 

 of the nature of smoke, rising up from the body of the 

 comet, and so illuminated by the light of the sun when 

 tolerably near it as to become visible. 



191. The Prindpia was published, as we have seen, in 

 1687. Only a small edition seems to have been printed, 

 and this was exhausted in three or four years. Newton's 

 earlier discoveries, and the presentation to the Royal 

 Society of the tract De Motu ( 177), had prepared the 

 scientific world to look for important new results in the 

 Prindpia, and the book appears to have been read by 

 the leading Continental mathematicians and astronomers, 

 and to have been very warmly received in England. The 

 Cartesian philosophy had, however, too firm a hold to be 

 easily shaken ; and Newton's fundamental principle, in- 

 volving as it did the idea of an action between two bodies 

 separated by an interval of empty space, seemed impossible 

 of acceptance to thinkers who had not yet fully grasped 

 the notion of judging a scientific theory by the extent 

 to which its consequences agree with observed facts. 

 Hence even so able a man as Huygens (chapter VIH., 

 154, 157, 158), regarded the idea of gravitation as 

 " absurd," and expressed his surprise that Newton should 

 have taken the trouble to make such a number of laborious 

 calculations with no foundation but this principle, a remark 

 which shewed Huygens to have had no conception that 

 the agreement of the results of these calculations with 

 actual facts was proof of the soundness of the principle. 

 Personal reasons also contributed to the Continental neglect 

 of Newton's work, as the famous quarrel between Newton 

 and Leibniz as to their respective claims to the invention 

 of what Newton called fluxions and Leibniz the differen- 

 tial method (out of which the differential and integral 

 calculus have developed) grew in intensity and fresh com- 

 batants were drawn into it on both sides. Half a century 

 in fact elapsed before Newton's views made any substantial 

 progress on the Continent (cf. chapter XL, 229). In our 

 country the case was different ; not only was the Prindpia 

 read with admiration by the few who were capable of 

 understanding it, but scholars like Bentley, philosophers 

 like Locke, and courtiers like Halifax all made attempts 



