

444 Mr. J. E. II. Gordon on Measuring the 



now have Vjp + K*. Similarly, when the want of sharpness i s 

 due to more than two causes, we must replace h by {2A 2 }^. 

 When, as often happens, the product of the quantities Jik . . . is 

 to be considered as given, the experiments are best arranged so 

 as to make the independent quantities equal ; for then the agree- 

 ment between the two curves is the closest. 



The practical rule to which we are led by the considerations 

 explained in this paper is therefore as follows :— 



Construct the curve representing the immediate results of the ob- 

 servations in the ordinary way. Let R m be any o rdinate. Draw 



parallels PM,QN at distances equal' to h, or {2h 2 }*, and join 

 P Q cutting R m in S. The point p on the true curve correspond- 

 ing to the abscissa m is to be found by taking p R equal to one 

 third of R S, and so that p and S lie on opposite sides of R. 



LVIII. On a Method of Measuring the Lateral Diffusion of a 

 Current in a Conductor by means of Equipotential Lines ; being 

 , a Note on a Paper by Dr. Macaluso "On the Transmission of 

 Electricity in Liquids" in the Philosophical Magazine for No- 

 vember 1871. By J. E. H. Gordon*. 



IN the abstract of Dr. Macaluso's paper given in the Phi- 

 losophical Magazine for November 1871, p. 389, it is 

 stated that "when an electric current travels through a liquid 

 whose cross section is much greater than the surface of the 

 electrodes, it tends to diffuse itself laterally." About two years 

 ago I made some experiments in the physical laboratory of 

 King's College, on the lateral diffusion of the current in con- 

 ductors. Instead of liquids, however, I used sheets of tinfoil of 

 various shapes. 



I was not on]y able to experimentally detect the lateral diffusion, 



but also to arrange a method by which its direction and amount 



may be measured. The outline of the method was suggested to 



me by a friend. I do not know whether it is new ; but as I have 



* Communicated bv the Author. 



