Royal Irish Academy. 593 



Cubic inches. 



Time, 2 minutes 1*6 



After 5 minutes 1*6 



" Third Experiment. — The zincs and platinized silver being re- 

 moved, the acid remaining untouched ; the platinized silver plates 

 were bent round the zincs. 



Cubic inches. 



Time, 2 minutes ......... 2*6 



After 5 minutes . . . . . . . ...... . 2*4 



" Fourth Experiment. — The platinized silver cut in two. 



Cubic inches. 



Time, 2 minutes 1*4 



After 5 minutes 1*4 



" Supposing, from these experiments, the same quantity of electri- 

 city to be developed, whichever of the opposed surfaces of the two 

 metals be the greater, I placed in separate glasses five zinc cylinders, 

 one-inch diameter, immerged eight-tenths of an inch in the acid ; 

 platina foil, connected by binding screws with the zincs, was rolled 

 into cylinders two-tenths of an inch in diameter, and then immersed 

 in pipeclay tubes one inch deep. 



Cubic inches. 



Time, 2 minutes 1*0 



After 10 minutes TO 



" Second Experiment. — Platina foil of the same size as the zincs, 

 and zinc rods of the same diameter as the platina cylinders being 

 employed, the effects were precisely the same. 



Cubic inches. 



Time, 2 minutes 1*0 



After 10 minutes 1*0 



" Third Experiment. — The zinc cylinders being made twice the 

 diameter of the former ; the quantity of gas generated in two minutes 

 was the same as before ; the increased number of lines of electrical force 

 compensating the increased resistance offered by the acid solution. 



" Fourth Experiment. — With cylinders twice the diameter of these, 

 a very feeble current passed, the obstacle being too great to be over- 

 come ; by increasing the diameter of the porous vessels, and thereby of 

 the nitric acid solution, which is a good conductor, the impediment is 

 diminished, as shown in experiment fifth. Thus Mr. Binks (Phil. Mag., 

 S. 3. vol. xi. p. 68) finds, that in dilute sulphuric acid, the size of the 

 copper compared to a given surface of zinc, to produce a maximum 

 effect, should be 1 6, that of the zinc to a given surface of copper being 

 7 ; while in a galvanic arrangement, in which the zinc is immersed in 

 dilute sulphuric acid enclosed in a membranous bag, and the copper 

 in a surrounding solution of sulphate of copper, the proportion of 

 zinc to copper was as one to eight, the impediment to the passage of 

 the current being double in the latter case what it was in the former*. 



* ** The experiments of Prof. Daniell have proved, that in the constant 

 battery, when the generating surface formed the circumference of the ar- 

 rangement, the force was only the half of that evolved when it formed the 

 centre." — Phil. Trans., vol. cxxviii. p. 41. 



