SIMSON. 147 



passed through Glasgow on his way to France ; and 

 on his return he communicated to Dr. Simson without 

 demonstration a proposition concerning conies derived 

 from it, which led his friend to insert some important 

 investigations in his Conic Sections. In 1723 the 

 publication of his paper took place in the Philosophical 

 Transactions ; it is extremely short, and does not ap- 

 pear to contain all that the author had communicated ; 

 for we find this sentence inserted before the last por- 

 tion of the paper : " His adjecit clarrissimus professor 

 propositiones duas sequentes libri primi Porismatum 

 Euclidis, a se quoque restitutas." The paper contains 

 the first general proposition and its ten cases, and then 

 the second with its cases. No general description or 

 definition is given of Porisms ; and it is plain that 

 his mind was not then finally made up on this obscure 

 subject, although he had obtained a clear view of it 

 generally. 



At what time his knowledge of the whole became 

 matured we are not informed ; but we know that his 

 own nature was nice and difficult on the subject of his 

 own works ; that he never was satisfied with what he 

 had accomplished ; and he probably went on making 

 constant additions and improvements to his work. 

 Often urged to publish, he as constantly refused ; in- 

 deed he would say that he had done nothing, or next 

 to nothing, which was in a state to appear before the 

 world ; and moreover, he very early began to appre- 

 hend a decay of his faculties, from observing his recol- 

 lection of recent things to fail, as is very usual with 

 all men ; for as early as 1751, we find him giving this 

 as a reason for declining to undertake a work on Lord 

 Stanhope's recommendation, when he was only in his 

 sixty-fifth year. Thus, though he at first used to say 

 he had nothing ready for publication, he afterwards 

 added, that he was too old to complete his work satis- 

 factorily. In his earlier days he used occasionally to 

 affect a kind of odd mystery on the subject, and when 



