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LXXIII. On the Luminous Phenomena of the Voltaic Battery. 

 By M. Van Breda. {Extract of a Letter to M. Arago*.) 



« # * * 



I SHOULD have preferred deferring the coramu- 

 •*■ nication which I have now the honour to lay 

 before you, of the results to which I have been led by the 

 study of the phsenomena accompanying the transfer of par- 

 ticles between metallic points, spheres or plates, by an ener- 

 getic galvanic current. 



" The investigation of the molecular phsenomena, which I 

 have undertaken with the aid of the powerful apparatus in the 

 Teylerian Museum, is still far from being finished; but as I 

 find in the Comptes Rendus, tome xxii. p. 690, an extract of a 

 memoir by M. De la Rive on the same phsenomena, and that 

 its illustrious author there communicates some results which 

 appear to me not wholly to coincide with what my experi- 

 ments have indicated, I think it may be useful for science to 

 transmit to you some of the principal facts at which I have 

 arrived, deferring to give them more in detail when I shall 

 have finished several other experiments, the apparatus for 

 which is constructing. 



" The battery, on Grove's construction, in the Teylerian 

 Museum, is composed of sixty pairs, the elements of which have 

 a surface of forty- five English square inches. 1 had first an 

 apparatus made by means of which I could produce the lumi- 

 nous arc at the focus of a microscope. I moved a metallic 

 point under the microscope, one while towards a similar point, 

 then towards a metallic plate. The movement was effected 

 by means of a screw micrometer, which enabled me to appre- 

 ciate the hundredths of a millimetre. 



" I could never obtain the transfer of matter without a 

 previous contact, and in this I am in perfect agreement with 

 the illustrious Genevese professor. I held the two very elon- 

 gated points at a distance from one another, not exceeding 

 ^uth of a millimetre, without ten elements of my large pile 

 being able to produce a commencement of transference. As 

 soon as contact has taken place the current passes ; but like- 

 wise instantly ceases when the points are very much attenuated 

 [effilees], because their ends are fused and repelled along the 

 electrodes, — a phsenomenon connected with another, of which 

 I shall speak hereafter, and to which I shall return in a sub- 

 sequent memoir. 



" When however I employed ten elements of ordinary 

 dimension, the current continued after the contact; and I 

 observed very well under the microscope what passes when 

 * From the Comptes Rendus for August 31, 1846. 



