70 GREEK GEOMETRY. 



The time bestowed on this useful work was no less than nine 

 years, It only was published in 1758. To the second 

 edition, in 1762, he added a similarly correct edition of the 

 Data, comprising several very valuable original propositions 

 of his own, of Mr. Stewart, and of Lord Stanhope, together 

 with two excellent problems to illustrate the use of the Data 

 in solutions. 



We tb-Tis find Dr. Simson employed in these various works 

 which he successively gave to the world, elaborated with 

 infinite care, and of which the fame and the use will remain 

 as long as the mathematics are cultivated ; some of them 

 delighting students who pursue the science for the mere 

 speculative love of contemplating abstract truths, and the 

 gratification of following the rigorous proofs peculiar to that 

 science; some for the instruction of men in the elements, 

 which are to form the foundation of their practical applica- 

 tions of geometry. But all the while his mind never could 

 be wholly weaned from the speculation which had in his 

 earliest days riveted his attention by its curious and sin- 

 gular nature, and fired his youthful ambition by its diffi- 

 culty, and its having vanquished all his predecessors in 

 their efforts to master it. We have seen that as early 

 as 1715 at the latest, probably much earlier, the obscure 

 subject of Porisms had engaged his thoughts ; and soon 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 conveyed no precise information; the hiatus in the 

 account which 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 descried to 

 guide the inquirer for the first porism of the first book alone 

 remained entire, the general porism being given wholly trun- 

 cated (mancum et imperfectum) all seemed to present ob- 

 .stacles wholly insurmountable ; and after various attempts for 



