382 Institute of France, 



described which possessed no powers of any kind ; yet it was 

 shown tliut the component metals were of the most energetic 

 kind, that the menstruum was very powerful with other metallic 

 combinations, and that the want of energy did not depend on a 

 balance of electro-motive power between the metals and men- 

 struum. It was then shown that the plates of Volta, commonly 

 urged as a proof that the evolution of electricity in Galvanic ex- 

 periments does not dc})cnd on chemical action, afford no evi- 

 dence, and that they have even no connexion with the question. 



A review was then taken of the different Voltaic arrangements 

 which have been discovered by philosophers, and it was shown 

 that not one of tiieui contradicts the statement that chemical 

 action is the means by which Galvanic phsnomc-na are pro- 

 duced : for, in every arrangementt hat possessed activity, chemi- 

 cal action of some kind was going forward. 



The paper throughout the whole was illustrated by numerous 

 experiments performed before the Society. 



On Wednesday, May 17, the Society adjourned during the 

 summer recess. 



FUENCH INSTITUTE. 



Department of Mathematics f drawn up ly ChevalierDELAUBKEf 

 perpetual Secretary. 



[Continued from p. 313.] 



\^ c have already, in our notice for last year, I)riefly analysed 

 the memoir of M. Biot, on a new application of the theory of 

 the oscillations of light, read to the Class at the latter end of 

 1813. The author there announces that he has extended to the 

 .substaaces of which the double refraction is the most energetic, 

 such as arragonite and rhomboidal carbonated lime, the inquiries 

 which he had only applied at first to substances the double re- 

 fraction of which is so weak that tlie images of the luminous 

 points, seen through glasses of parallel surface three or four 

 centimetres thick, are not sensibly separated. He has found in 

 this way, that in these crystals, as in al! the others, the luminous 

 molecules begin by oscillating around their centre of gravity to 

 a certain depth, after which they acquire also a fixed polariza- 

 tion, which ranges their axes in two rectangular directions. 



In order to observe these phajnomena in any given crystal, 

 we must attenuate its polarizing power, until the luminous mo- 

 lecules which pass through it make in its interior eight oscilla- 

 tions less. We attain this either by forming with the givpn cry- 

 stal laminae sufficiently thin, or by inclining them on an incident 

 polarized ray, .so as to diminish the angle which the refracted 

 ray forms with the cij.\is of double refraction 3 or, finally, (and 



which 



