472 



rent from the platiiia battery destroyed the deflection of the 

 needle produced by the current from the leaden one, and caused 

 an opposite deflection, which indicated that the former current 

 was nearly twice as strong as the latter. The two batteries 

 were allowed to work for three hours and a half. At the end 

 of that time the current from the lead was more than twice as 

 strong as the current from the platina. The quantity of lead 

 dissolved during these three hours and a half was very small. 



" It struck me that, by diminishing the action of the acids 

 on the lead, I might increase the power of the battery. I there- 

 fore covered a plate of lead with gold-leaf, and coated another 

 of the same size with chloride of gold, in the same way in 

 which sheet silver is platinized for Smee's battery. These 

 two, and a platina plate of the same size, were put successively 

 into a porous cell of a Grove's battery, and the voltaic cur- 

 rent was sent through the helix of our large electro-magnet, 

 in which the iron bar is about thirteen feet long, and two and 

 a half inches thick, the copper wire is about 500 feet long, and 

 one-sixth of an inch in diameter. The magnetic power given 

 to the electro-magnet by the leaden plate coated with chloride 

 of gold, appeared to be fully equal to that produced by the pla- 

 tina plate : the magnetic efi'ect of the current from the leaden 

 plate covered with gold-leaf was not so great. Platinized lead 

 produced as strong a current as platina, or as lead coated with 

 chloride of gold. 



" On last Friday week, a leaden and platina battery of equal 

 size were left working for four hours and a half. At the end 

 of that time the plate of lead acted fully as well as the platina 

 plate. When the nitric acid was so much exhausted that the 

 lead was barely capable of magnetizing the large electro- 

 magnet, so as to sustain a certain weight, the leaden plate was 

 taken out of the porous cell, and a platina plate of the same 

 size put in its place. The platina plate was not able to make 

 the electro-magnet sustain the weight which the lead caused 

 it to sustain. 



