398 D'ALEMBERT. 



which he had so often found delight, long after he had 

 held the highest offices and been engaged in the most dis- 

 similar discussions. As late as 1838, when I was en- 

 gaged in preparing my Analytical Review of the Prin- 

 cipia, I found that, by an accidental coincidence, he was 

 amusing his leisure with the calculus long intermitted; 

 and I am sure that he could have furnished as correct 

 and more elegant analytical demonstrations of the New- 

 tonian theorems than I had the fortune to obtain in com- 

 posing that work. 



I have thought it a useful thing to consider the per- 

 sonal history with the scientific achievements of a very 

 great geometrician, with a view to the illustration of 

 these remarks and I have chosen D'Alernbert in pre- 

 ference to Euler or to Clairaut, the two other illustrious 

 analysts of their age, because we have more ample 

 materials for the study. Whatever of peace and comfort 

 he enjoyed, D'Alembert owed to geometry, and confessed 

 his obligations. Whatever he suffered from vexation of 

 any sort, he could fairly charge upon the temporary in- 

 terruption of his mathematical pursuits. In both por- 

 tions of his history, therefore, it is likely to prove instruc- 

 tive, and to enforce the doctrine which I have laid down. 



Jean le Rond d'Alembert was born on the 17th of 

 Nov., 1717, being a foundling exposed near the church 

 of St. Jean le Rond in Paris, and thus called by the 

 name of the parish, as is usual in most countries. The 

 commissary of the district, before whom the infant was 

 carried, perceiving its feeble and almost dying condition, 

 instead of sending it to the hospital gave the charge to 

 the wife of a poor but honest glazier in the neighbour- 

 hood, living in the Rue Michel-le-Comte, for he was ac- 



