475 



very cheap compared with the latter : a plate of platinized or 

 gilded lead, one foot square, may be made for a shilling, but 

 a platina plate of the same size will cost nearly three pounds ; 

 secondly, the expense of working the former for any time is 

 much less than the expense of working the latter for the same 

 time ; thirdly, the nitre leaden battery does not emit fumes of 

 nitrous gas. 



" The leaden battery, when charged with nitro-sulphuric 

 acid, appears not to exhaust the nitric acid so rapidly as the 

 platina battery ; probably, a good deal of the hydrogen, which 

 would otherwise unite with the oxygen of the nitric acid, is 

 dissipated by the gold or platina powder on the surface of the 

 lead. 



" The advantage of the platinized or gilded leaden battery 

 over Smee's battery, is, that platinized or gilded lead costs far 

 less than platinized silver. A plate of the former, six inches 

 square, will not cost more than three-pence, whilst a plate of 

 the latter of the same size, will cost about three shillings. 



" 1 shall now mention a few more experiments which I have 

 made with the leaden and platina batteries. I compared their 

 power in magnetizing our large electro-magnet, and in pro- 

 ducing heat. The magnetic power and heat produced by the 

 platina, excited by concentrated nitric and sulphuric acid, was 

 equal to that produced by the platinized lead excited by a 

 mixture of nitre and sulphuric acid diluted with an equal bulk 

 of water. Each of the batteries fused the thinner of the two 

 wires which I enclose. In each battery there was but a sin- 

 gle voltaic circle. The platina and leaden plates contained 

 each about ten square inches; they vvere about five inches 

 long and two broad. Neither of these batteries was able to 

 fuse the thick wire; but when about a tea-spoonful of nitric 

 acid was pouredinto the cell containing the leaden plate, and 

 the current sent through the thick wire, it was fused. The 

 platina battery only raised the thick wire to a white heat. 

 Hence, 1 infer that platinized lead, excited by a mixture of 



