330 Mr. W. Grant on the Curves of 



Hence, in gaseous as well as in liquid electrolytes, metals, 

 unless touching, are at different potentials, dependent on this 

 mutual influence as well as on the amount of chemical action 

 set up by the one, more electro-negative, which becomes 

 negative to the electrolyte, and still more so to the electro- 

 positive metal. 



As a conclusion, these two points, I fancy, hold generally 

 for gases and liquids: — 



(i) The metal to which goes the electro- \ P 0S1 !T e ion 

 v J to ( negative 



becomes, by the charges brought by the dissociated atoms, 



electro- / positive re i a ti ve ly to the electrolyte ; and 

 ( negative J J 



(ii) Metallic contact entails equality of potential. 



The simplicity of these laws is evident, as also the advan- 

 tage of bringing back to generally received laws of action the 

 phenomena of potential due to contact of metals and electro- 

 lytes. 



I wished to have added one or two experiments to the above, 

 which I wanted also to repeat to get surer quantitative deter- 

 minations, and to render the conditions more conducive to 

 accuracy; but the time at my disposal was limited, as well as 

 the opportunities for performing the experiments. 



St. John's College, October 1881. 



XLIII. On Curves of Electromagnetic Induction. 

 By W. Grant *.. 



[Plates IX., X., & XL] 



IN the month of June 1879 I communicated to the Physical 

 Society a series of measurements of ihe conjugate posi- 

 tions of two equal circular coils f of wire whose axes were 

 parallel to each other — that is to say, measurements of the rela- 

 tive positions of the coils when they were so placed that their 

 coefficient of mutual induction became nothing. I also showed 

 how, by the aid of these measurements, a curve could be 

 drawn such that when one coil remained fixed, and the other 

 was moved with its centre always in the curve and its axis 

 parallel to that of the first coil, the mutual induction between 

 the coils retained the constant value zero. An obvious exten- 

 sion of this investigation was to try to trace out some of the 



* Communicated by the Physical Society of London, having been read 

 June 11th, 1881. 



t Phil. Mag. for November, 1879. 



