448 Notice of some Recent 



while it exercises a very great influence upon the intensity 

 of the dynamical effects, and so much the stronger in pro- 

 portion to the goodness of the conductors ; he has deduced 

 some practical consequences applicable to a more advan- 

 tageous construction of a voltaic pile in each particular case. 

 4. The examination which he has made of the influence 

 of metallic diaphragms, placed either on the track of a 

 current between the poles of a pile, or in the interior of a 

 pile itself, has shewn that this influence is very different 

 according to the nature of the conductors placed between 

 the poles, and may be explained by a greater or less altera- 

 tion in the conductibility of the homogeneous conductors 

 in which the diaphragms are placed. 5. In endeavouring 

 to appreciate in all its extent, the influence of a number of 

 pairs, De La Rive has observed, that the number sometimes 

 increases, sometimes diminishes the intensity of the effects 

 of a pile, and that these variations depend on several circum- 

 stances belonging, some to the pile, others to the nature of 

 the conductors interposed between the piles. He infers 

 from the study of these circumstances, that the phenoniena 

 to which they give birth are a consequence of the chemical 

 theory of the pile.* 



CHEMISTRY. 



Composition of atmospheric air . — M. T. de Saussure has 

 taken advantage of the property which small shot pos- 

 sesses of absorbing oxygen when moistened and agitated 

 with atmospheric air at common temperatures, to analyze 

 common air. He employed a matrass possessing a capacity 

 of from 150 to 250 centi-metres cubes closed hermetically 

 with a metallic stopper, which is fastened with screws to 

 a firm socket at the end of the neck of the matrass. The 

 lead shot ought to contain 80 to 100 shots to the gramme, 

 (15*438 grs.) Its weight is nearly the fifth of that of the 

 water which the matrass contains. The water for moisten- 

 ing the shot should be equal to the seventeenth of its 

 weight. A larger or smaller quantity retards the oxida- 

 tion. Three hours of constant agitation are sufficient to 

 deprive the air of its oxygen. Saussure measures the quan- 

 tity of oxygen absorbed by the weight of the water which 



* Ann. de Chim. Ixii. 206. 



