472 
rent from the platina 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 anda 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 effect 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, 
