394 D'ALEMBERT. 



the Preliminary Discourse to the works of the Society for 

 the Diffusion of Useful Knowledge, and in the Introduc- 

 tion to the * Political Philosophy/ It never had been 

 stated, as far as I know, before; but it rests on such 

 irrefragable principles, that it has not since been called 

 in question.* 



It is an illustration of the happiness derived from 

 mathematical studies, that they possess two qualities in 

 the highest degree, not perhaps unconnected with one 

 another. They occupy the attention, entirely abstracting 

 it from all other considerations ; and they produce a calm 

 agreeable temper of mind. 



Their abstracting and absorbing power is very remark- 

 able, and is known to all geometricians. Every one has 

 found how much more swiftly time passes when spent in 

 such investigations, than in any other occupation either 

 of the senses or even of the mind. Sir Isaac Newton is 

 related to have very frequently forgotten the season of 

 meals, and left his food awaiting for hours his arrival 

 from his study. A story is told of his being entirely 

 shut up and disappearing, as it were eclipsed, and then 

 shining forth grasping the great torch which he carried 

 through the study of the heavens ; he had invented the 

 Fluxional Calculus. I know not if there be any founda- 

 tion for the anecdote ; but that he continually remained 

 engaged with his researches through the night is certain, 



* It gave me great pleasure to find it highly approved by my 

 revered friend, Professor Stewart, who regarded it as indeed of more 

 value and originality than I had considered myself. The outline 

 of it had been read many years before (1798) in a literary society 

 at Edinburgh, to which Lord Jeffrey, Dr. Brown, Mr. Horner, and 

 others belonged. See Appendix to this Life. 



