56 MR. DANIELL ON VOLTAIC COMBINATIONS. 



The principal circumstance which might be supposed to limit the power of an ac- 

 tive point within a conducting sphere in any given electrolyte, is the resistance of that 

 electrolyte, which increases in a certain ratio to its depth or thickness ; and this 

 thickness may be considered virtually the same, wherever the included point may 

 be placed, but to increase with the diameter of the sphere. It is also the same, and 

 consequently the resistance is also the same, when placed anywhere within the 

 plane which divides the sphere into two hemispheres. But in an insulated hemi- 

 sphere, the approximation of the active point to the lower surface virtually decreases 

 the thickness of the electrolyte through which its action has to be propagated, by 

 increasing the extent of surface which cuts the divergent lines of force ; and conse- 

 quently the force increases. In this respect the action of a point upon a plate may 

 be considered the same as upon an indefinitely large hemisphere, towards which as 

 the point approaches the force increases. 



It appears to me that practical consequences of some importance flow from the 

 preceding conclusions, upon which I may be tempted to address you again at no 

 distant period. 



I remain, my dear Faraday, 



Ever faithfully yours, 



J. F. Daniell. 

 King's College, 

 January 13, 1838. 



