556 REPORT — 1881. 



difference in tlieir capillary relations. In investigating this action I used a capillary 

 tube in ■which was a thread of mercury broken by an air-bubble, and by causing 

 this to run, I found that oxidation took place at the concave surface of tiie retreat- 

 ing coluuin and rendered it negative to the advancing convex siu-face. I thus, 

 obtained as much as -70 as the difference in potential (by increasing the number of 

 bubbles), while in tlie case of the falling drops a deflection indicating from -50 to 

 •6D existed. The connection between this and oxidation was rendered evident by 

 the possibility of increasing the deflection obtained by more rapid oxidation, and 

 of reversing it by substituting for air a reducing gas, "while if both funnel and jet 

 were in an inert medium the absence of deflection would prove the second point: 

 metals, when touching, are at the same potential. 



11. On the Electric Discharge through Colza Oil} 



Bij A. Macfarlane, M.A., D.Sc, F.E.S.E. 



The electrical properties of colza oil examined were its dielectric strength and 

 some phenomena accompanying the passage of the spark. By the dielectric 

 strength of a substance is meant the ratio of the difference of potential required 

 to pass a spark through the substance to that required to pass a spark through' 

 air under the same conditions. One set of observations gave 2-7 as the value for 

 colza oil ; another gave 2-5. The values now obtained for liquids are exhibited in 

 the following table : — 



Substance Dielectric strength 



Paraffin oil 3-7 



Oil of turpentine 4-0 



Paraffin (liquefied) 2-4 



Olive oil 3-5 



Colza oil 2'6 



The passage of the spark was accompanied by the formation of gas-bubbles, but 

 there was no deposition of solid particles. The behaviour of these bubbles was 

 such as to indicate that they were formed at the positive electrode, and that they 

 were positively electrified. 



The method of the investigation is that described in ' Trans. R. S. E.,' vol. 

 xxviii. p. 633, 



12. Representation graphique cle la Fornmle des Piles.'^ Discmsion. Par 

 le Professeur C. M. Gakiel, Agrege de Physiipie a la Faculte de Medecine 

 de Paris, Inge'nieur des Ponts et Ghaussees. 



M. Gariel iudique une representation graphique de la formule bien connue qui 

 doime rintensit(5 d'uu courant, connaissaut le nombre des elements, la force 

 6lectromotrice, la resistance de chacun d'eux et la resistance ext(5rieure, et qui, 

 par une construction tres simple, permet de comparer cette intensite avec celle 

 que donnerait dans le meme circuit un seul (Sl^ment. Cette construction qui ne 

 comporte que le trac^ de lignes droites est susceptible d'etre donnee par un ap- 

 pareil m(Scanique fort simple qui fournit immediatement le resultat par une seule 

 lecture. 



Une discussion analogue permet d'(5tudier le cas ou les elements sont reunis en 

 quantitd et particulierement conduit a la solution du probleme suivant: 6tant 

 donnes un circuit et n elements egaux, comment faut-il les grouper en m groupes de 

 p Elements pour obtenir le courant maximum ? 



La regie est la suivante : — 



■ See Nature, vol. xxiv., p. 465. 



■ Le travail in externa a paru dans le journal franfais VElectricien, Nos. des 

 19 avril et ]" mai 1881. 



