MEMOIR ON LIGHT. 137 



The memoir of which I am speaking was destined for 

 the Institute of Egypt. I find in fact, in a letter from 

 Mains to Lancret, the following passage * 



" I send you, my dear Lancret, the work of which I 

 have already spoken : mark out for me those things in it 

 which any one might call repetitions of what has been 

 already said, or which are useless ; if, after this expurga- 

 tion, it should be reduced to zero, we will put it aside, 

 and there will be no more question about it." 



It is just to remark, after the critique from which I 

 could not abstain when I considered that my task was 

 not that of a panegyrist but of a biographer aiming at the 

 truth, that the third part of the memoir was written be- 

 fore the publication of the fourth volume of the Mecan- 

 ique Celeste, in which the same subject is treated with 

 the greatest care. I would add that no army in the 

 world ever before counted in its ranks an officer who 

 occupied himself in the spare hours of advanced posts 

 with researches so complete and so profound. The truth 

 of this remark is not affected by the recollection which it 

 brings up of the expedition of Alexander. It is true, 

 men of science, at the recommendation of Aristotle, then 

 accompanied the great general : but their mission was 

 solely to collect the scientific achievements of the con- 

 quered nations, and not to make advances in the sciences 

 by their own labours. This difference, altogether in 

 favour of the French army, deserves, I think, to be here 

 noticed.* 



I see by a letter of Lancret, of the 14th Vendemiaire,t 



* If this comparison were worth carrying out. the author might 

 have added that the men of science in Alexander's expedition were 

 not officers of the army charged at the same time with onerous and 

 hazardous duties, but leisurely investigators, having no other occupa- 

 tion. Translator. 



t October 5, 1800. 



