• Eloge of Alexander Volta. 



any kind; without absorbing it ; and that oxygen, in fine, occu- 

 pies so important a place in the phenomena of vegetation, — we 

 may imagine that in course of time the atmosphere varies consider- 

 ably in its composition ; that it will one day be unfit for respira- 

 tion ; that then all animals will be annihilated, not in consequence 

 of one of those physical revolutions of which geologists have found 

 -so many indications, and which, in spite of their immense extent, 

 may leave a chance of safety to some individuals favourably si- 

 tuated ; but by a general and inevitable cause, against which 

 the frozen zones of the poles, the burning regions of the equa- 

 tor, the immensity of the ocean, the prodigiously elevated plains 

 of Asia and America, the snowy summits of the Cordilleras and 

 of the Himalaya, would be equally unavailing. To study all the 

 particulars, as well as the actual period of that grand pheno- 

 menon, to collect the exact data that future ages will supply, 

 is the task that philosophers have been anxious to accomplish, 

 particularly since the eudiometer has given them the means of 

 doing it. To obviate some objections to which the first trial 

 of this instrument gave rise, MM. de Humboldt and Gay- 

 Lussac submitted it to the most scrupulous examination. When 

 such judges declare that none of the eudiometers approach in ac- 

 curacy to that of Volta, we are no longer at liberty to doubt the 

 fact. 



Since I have abandoned chronological order, before occu- 

 pying myself with the most important works of our venerable 

 confederate, before analysing his researches regarding atmosphe- 

 ric electricity, and characterizing the discovery of the pile, I 

 shall mention in few words the experiments that he published in 

 the year 1793, on the expansion of air. 



This important question had attracted the attention of a great 

 number of able natural philosophers, who did not agree either up- 

 on the total increase of volume the air undergoes between the 

 temperatures of melting ice and the boiling point ; nor upon the 

 gradations of expansion in the intermediate temperatures. Volta 

 discovered the cause of these disagreements : he shewed that in 

 operating in a vase containing water, increasing expansions should 

 be found ; that if there is no other humidity than that with which 

 vitreous partitions are generally covered, the apparent expansion 

 «Gf the air should increase in the lower parts of the thermometric 



