380 Anniversary Meeting. [Nov. 30, 



due to him, cheerfully undertook the printing of the 'Principia' 

 at his own expense, and entered instantly on the duty of editing 

 it with admirable zeal and energy, involving, as it did, expostu- 

 lations, arguments, and entreaties to Newton not to cut out 

 large parts of the work which he wished to suppress* as being 

 too slight and popular, and as being possibly liable to provoke 

 questions of priority. It was well said by Rigaud, in his ' Essay 

 on the first publication of the Principia,' that " under the cir- 

 cumstances, it is hardly possible to form a sufficient estimate of 

 the immense obligation which the world owes in this respect to 

 Halley, without whose great zeal, able management, unwearied 

 perseverance, scientific attainments, and disinterested generosity r 

 the * Principia ' might never have been published. "f Those who 

 know how much worse than "law's delays" are the troubles,, 

 cares, and labour involved in bringing through the press a book 

 on any scientific subject afc the present day will admire Halley'a 

 success in getting the ' Principia ' published within about a year 

 after the task was committed to him by the Royal Society, two 

 hundred years ago. 



When Newton's theory of universal gravitation was thus made 

 known to the world Descartes' Vortices, an invention supposed to be 

 a considerable improvement on the older invention of crystal cycles 

 and epi-cycles from which it was evolved, was generally accepted, 

 and seems to have been regarded as quite satisfactory by nearly all 

 the philosophers of the day. 



The idea that the Sun pulls Jupiter, and Jupiter pulls back against 

 the Sun with equal force, and that the Sun, Earth, Moon, and Planets 

 all act on one another with mutual attractions, seemed to violate the 

 supposed philosophic principle that matter cannot act where it is 

 not. Descartes's doctrine died hard among the mathematicians and 

 philosophers of Continental Europe ; and for the first quarter of last 

 century belief in universal gravitation was an insularity of our 

 countrymen. 



from Halley requesting Boyle, then at Rotterdam, to do all in his power to give 

 publicity to the book. "When the Society resolved on Halley's undertaking to 

 measure a degree of the Earth, it was voted that " he be given 50 or fifty * Book& 

 of Fishes' " (Weld's 'History of the Koyal Society,' vol. 1, p. 310). 



* " The third [book] I now design to suppress. Philosophy is such an imper- 

 tinently litigious lady that a man had as good be engaged in lawsuits as have to do 

 with her. I found it so formerly, and now I am no sooner come near her again 

 but she gives me warning. The first two books without the third will not so well 

 bear the title of ' Philosophise Naturalis Principia Mathematical and therefore I 

 have altered it to this, ' De Motu Corporum Libri duo " ; but, upon second thoughts, 

 I retain the former title. 'Twill help the sale of the book, which I ought not to 

 diminish now 'tis yours" (ibid., p. 311). 



t Ibid., p. 310. 



