SIMSON. 495 



the general one. A note among his memoranda ap- 

 pears to have been made, as was his custom, of the 

 date at which he succeeded in any of his investiga- 

 tions.* " Hodie heec 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 

 passed through Glasgow on his way to France ; and 

 on his return he communicated to Dr. Simson with- 

 out 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 appear to contain all that the author had 

 communicated ; for we find this sentence inserted 

 before the last portion of the paper : " His adjecit 

 clarissimus 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. 



* 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 



UOctobr. 1764. 

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



Laus et gloria. 77 (sell. Anno jEtatis.) 



