SIMSOX. 493 



after, his mind was so entirely absorbed by it that he 

 could apply to no other investigation. The extreme 

 imperfection of the text of Pappus, the dubious nature 

 of his description, his rejection of the definition which 

 appeared intelligible, his substituting nothing in its 

 place except an account so general that it really con- 

 veyed no precise information, the hiatus in the account 

 he subjoins of Euclid's three books, so that even with 

 the help of the lemmas related to these propositions of 

 the lost work, no clear or steady light could be de- 

 scjied to guide the inquirer for the first porism of 

 the first book alone remained entire, the general 

 porism being given wholly truncated (mancum et im- 

 perfectum) all seemed to present obstacles wholly 

 insurmountable, and after various attempts for years 

 he was fain to conclude with Halley that the mystery 

 belonged to the number of those which can never be 

 penetrated. 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 com- 

 pelled 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 found access to 



* " Firmiter animum induxi hsec nunquam in posterum investi- 

 gare. Unde quoties menti occurrebant, f oties eas arcebam." (Op. 

 Eel. 320. Prsef. ad Porismata.) 



