[ 330 ] 



XLY. On the Influence of Liglit on Electrical Tension 

 in Metals. By R. BoENSTEIN *. 



EECENT experiments have undoubtedly established the 

 fact that luminous radiation produces on the electrical 

 behaviour of metals an effect which cannot be due merely to 

 an elevation of temperature. This action takes place in two 

 ways, either producing a change in the electrical resistance 

 (a diminution) or a change in the electrical tension. In a 

 former paper f the author has given a summary of the results 

 obtained by other observers with respect to the dependence 

 of the resistance on the illumination. On the subject of a 

 change of electrical tension produced by illuminatiouj experi- 

 ments have been made by BecquerelJ, Grove §, Pacinotti||, 

 Hankel% and Adams and Day**. 



The first four of these observers examined into the electrical 

 phenomena v/hich were presented when, of two plates of the 

 same metal plunged in the same liquid, one was illuminated 

 while both were connected with the terminal wires of a sensi- 

 tive galvanometer. Under these conditions different kinds 

 of light were found to produce distinct variations in the che- 

 mical action ; and this difference of chemical action caused the 

 illuminated plate to acquire an electrical state opposite to that 

 of the unexposed one ; and consequently an electrical current, 

 which could be measured by a galvanometer, Avas generated 

 between the two plates. In the papers of Grove, Pacinotti, 

 and TIankel we find descriptions of the changes which took 

 place when conductible heat instead of light was allowed to 

 act upon one of the metal plates. Grove found that heat 

 produced no effect when acting upon one of two platinum 

 plates standing in Avater slightly acidulated ; he attributes the 



* Translated by E. E. Day, M.A. 



t Der Einjluss des Lichtes auf den eleJctrischen Leituyigsivider stand von 

 Metallen. Heidelberg : Carl Winter's Universitatsljuclihandlung. 8vo, 

 1877. 



X Becquerel, Comptes Jle7idm,t. ix. pp. 145, 561 (1839) ; t. xiii. p. 198 ; 

 Bihliot/i. Univ. de Geneve, nouv. ser. t. xxxv. p. 136 (1841) ; Ann. de 

 Chiniie et de PIit/s. (3) t. ix. p. 257 (1843) ; Comptes Bendus, t. xiv. p. 901 ; 

 Bihlioth. Univ. de Geneve, nouv. ser. t. xl. p. 341 (1842) ; Compt. Rend. 

 t. xxxii. p. 83 ; Ann. de CTiim. ct de Phys. (3), t, xxxii. p. 176 (1851). 



§ Grove, Report of tlie Meeting of the British Association, Leeds, 

 Sept. 1858 ; also Phil. Mag. (4) vol. xvi. p. 426 (1858). 



II Pacinotti, Cimento, t. xviii. p. 313(1863). 



^ W. Ilankel, Sitzungsher. der math.-phys. Kl. der k. Sachs. Gcs. d. W. 

 (1875); Annalen der Fhijsik und Chemie (neiie Folge), heraiisgeg. von 

 Wiedemann, Bd. i: S. 402 (1877). 



** Adams and Day, Proc. Roy. Soc. vol. xxxv. No. 172, p. 113 (1876). 



