PRESIDENTIAL ADDRESSES. 533 



at his own expense, and entered instantly on the 

 duty of editing it with admirable zeal and energy, 

 involving, as it did, expostulations, arguments, and 

 entreaties to Newton not to cut out large parts of 

 the work which he wished to suppress 1 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 circumstances, 

 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, scien- 

 tific attainments, and disinterested generosity, 

 the Principia might never have been published." 2 



1 "The third [book] I now design to suppress. Philosophy is 

 such an impertinently 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 Philosophic Naturalis Principia Mathe-. 

 malica, 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" (Weld's History of the Royal Society, vol. i. p. 311).. 



'-Ibid., p. 310. 



