146 SIMSON. 



piece of chalk ; he felt assured that he had now the 

 means of solving the great problem ; and although he 

 afterwards tells us that he then had not a sufficiently 

 clear notion of the subject (eo tempore Porismatum 

 naturam non satis compertam habebam),* yet he accom- 

 plished enough to make him communicate a paper 

 upon the discovery to the Koyal Society, the first 

 work he ever published (Phil. Trans, for 1723). He 

 was wont in after life to show the spot on which the 

 tree, long since decayed, had stood. If peradventure 

 it had been preserved, the frequent lover of Greek 

 geometry would have been seen making his pilgrimage 

 to a spot consecrated by such touching recollections. 

 The graphic pen of Montucla, which gave such interest 

 to the story of the first observation of the transit of 

 Venus by Horrox in Lancashire, and to the Torricellian 

 experiment,! is alone wanting to clothe this passage in 

 colours as vivid and as unfading. 



This great geometrician continued at all the intervals 

 of his other labours intently to investigate the subject 

 on which he thus first threw a steady light. 



His first care upon having made this discovery was to 

 extend the particular propositions until he had obtained 

 the general one. A note among his memoranda appears 

 to have been made, as was his custom, of the date at 

 which he succeeded in any of his investigations. J 

 " Hodie hsec de porismatis inveni, R. S., 23 April 

 1722." Another note, 27th April, 1722, shows that 

 he had then obtained the general proposition ; he 

 afterwards communicated this to Maclaurin when he 



* Op. Eel. 320. t Hist, de Math. vol. i. 



J In one there is this note upon the solution of a problem of tactions, 



" Feb. 9, 1734 : Post horam primam ante meridiem ;" and much later 



in life we find the same particularity in marking the time of discovery. 



His birthday was October 14, and having solved a problem on that day, 



1764. he says ... ^ . , -_,,, 



9 14 Octobr. 1 1 64. 



Deo Opt. Max. benignissimo Servatori 14 Octobr. 1687. 



Laus et gloria. 77 (scil. 



