26 



at the otherat right angles. Along the side of the tube also 

 holes are bored at distances corresponding to the distances 

 of the porous vessels from each other ; so that, upon pour- 

 ing nitric acid into the tube, the vessels are all filled at the 

 same moment ; when filled, the entire apparatus is placed in 

 a vessel containing sulphuric acid. The advantages of this 

 arrangement veere, that I had only two solutions to pour in, 

 whatever number of alternations were employed ; a sufficient 

 supply of acid solutions to keep up a constant action for a 

 length of time ; and a distance between the plates scarcely 

 exceeding the thickness of the porous vessel employed. 



" The following experiments were undertaken with the 

 intention of estimating the relative values of the different con- 

 structions of Grove's battery, recommended by Mr. Knight 

 of Foster Lane, as far as respects the arrangement of the 

 zinc and platina plates, when, to my surprise, I found the 

 same quantity of electricity to be evolved when the zinc is 

 bent so as to expose an opposing surface to each surface of 

 a platinum plate, as when a platinum plate, of the size of 

 the former zinc, is similarly placed with respect to a plate of 

 zinc of the same size as the former platinum, affording an 

 economical method of arranging a Wollaston's battery, the 

 zincs being bent round the coppers, in place of the coppers 

 round the zincs. 



" Experiments with Grove's Battery. 

 " The acid solutions were those recommended by Mr. 

 Grove, i. e. pure nitric acid, in contact with the platina ; sul- 

 phuric acid -}- 4-5 water by measure, in contact with the 

 zinc. The surfaces of zincs immersed were 3 by 2*5 inches ; 

 those of the platina, bent round the porous vessel holding 

 the zincs, were 6 by 2*.5 inches. The glasses containing the 

 acid, &c., were 3*2 inches long, I'd broad, 35 deep. The 

 length of the porous vessel of pipeclay was 2-5 inches, the 



