ANCIENT ANALYSIS. PORISMS. 71 



years he was fain to conclude with Halley that the mystery 

 belonged to the number of those which can never be pene- 

 trated. He lost his rest in the anxiety of this inquiry ; sleep 

 forsook his couch ; his appetite was gone ; his health was 

 wholly shaken ; he was compelled to give over the pursuit ; 

 he was "obliged," he says, "to resolve steadily that he never 

 more should touch the subject, and as often as it came upon 

 him he drove it away from his thoughts." * 



It happened, however, about the month of April, 1722, 

 that while walking on the banks of the Clyde with some 

 friends, he had fallen behind the company; and musing 

 alone, the rejected topic foxmd access to his thoughts. After 

 some time a sudden light broke in upon him ; it seemed at 

 length as if he could descry something of a path, slippery, 

 tangled, interrupted, but still practicable, and leading at least 

 in the direction towards the object of his research. He 

 eagerly drew a figure on the stump of a neighbouring tree 

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

 means of solving the great problem ; and although he after- 

 wards tells us that he then had not a sufficiently clear notion 

 of the subject (eo tempore Porismatum naturam non satis com- 

 pertani habebam),f yet he accomplished enough to make him 

 communicate a paper upon the discovery to the Eoyal 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 observa- 

 tion of the transit of Venus by Horrox in Lancashire, and 

 to the Torricellian experiment, J is alone wanting to clothe 

 this passage in colours as vivid and as unfading. 



* " Firmiter animum induxi hsec nunquam in posterum investigare. 

 Unde quoties menti occurrebant, toties eas arcebam." (Op. Rel. 320. 

 Praef. ad Porismata.) 



t Op. Kel. 320. J Hist, de Math. vol. i. 



