374 Messrs. C. R. A. Wright and C. Thompson. [June 20, 



fi lied with hydrogen, and an even number of doubly-coated porous 

 partitions. We found that the difficulty in avoiding leakage of gases 

 from one chamber to another and various other causes usually pre- 

 vented the E.M.F. of a battery of n doubly-coated plates from reach- 

 ing quite as high as n times the E.M.F. obtainable from a single cell ; 

 in no case did we obtain as high an E.M.F. as 1 volt per cell, even 

 with only infinitesimal currents, whilst 0'6 to 0*7 volt per cell was 

 about the highest valne obtained with currents of magnitude sufficient 

 to measure readily with the silver voltameter. Still our results were 

 sufficiently good to convince us that if the expense of construction 

 were no object, so that large coated plates could be employed, enabling 

 currents of moderate magnitude to be obtained with but small 

 current density, there would be no particular difficulty in construct- 

 ing " double aeration plate cells " of this kind, competent to yield 

 currents comparable with those derived from ordinary small labora- 

 tory batteries ; although we concluded that the economical production 

 of powerful currents for commercial purposes by the direct oxidation 

 of combustible gases did not seem to be a problem likely to be readily 

 solved, chiefly on account of the cost of the large appliances that 

 would be requisite. 



Precisely the same remark applies to all other forms of cell in 

 which oxidation is effected by means of atmospheric air applied as an 

 "aeration plate," at least, so far as our observations have extended. 

 Given sufficiently large aeration plates, there is no difficulty in setting 

 up aeration cells capable of producing moderately powerful currents, 

 the energy being due either to the oxidation of a metal (e.g., zinc or 

 aluminium, &c), or to the oxidation of an oxidisable fluid, such as 

 solution of sodium hyclrosulphite (Schutzenberger's), ammoniacal 

 cuprous oxide, and such like liquids. As yet we have not succeeded 

 in effecting the direct oxidation in this way of alcohol, petroleum, 



