82 The Rev. N. J. Callan on a new Voltaic Battery. 



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

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

 plates and a platina one of the same size were put successively 

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

 rent 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 diameter. The magnetic power given to 

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

 gold, appeared to be equal to that which was produced by the 

 platina plate. The magnetic effect of the current from the 

 leaden plate covered with gold leaf was not so great. A coat- 

 ing of chloride of platina was afterwards found to answer as 

 well as one of chloride of gold. 



Some days after a leaden and platina battery of the same 

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

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

 "When the nitric acid was so much exhausted that the lead 

 was barely capable of magnetizing the large electro-magnet so 

 as to make it 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 stead. The platina plate was not able to make 

 the electro-magnet sustain the weight which the lead had 

 caused it to sustain. 



The magnetizing power of the platinized or gilded lead and 

 platina batteries was compared several times in working an 

 electro-magnetic machine. On these occasions the power of 

 the leaden battery was evidently superior to that of the pla- 

 tina one. Sometimes the platina plate was taken out of the 

 porous cell, and a platinized or gilded lead plate of the same 

 size put in its place : the velocity of the machine was instantly 

 and considerably increased. The same effect was produced 

 when the platina plate was taken out of the cell and a plati- 

 nized platina one put in its stead. Hence it appears that a 

 leaden plate coated with chloride of platina or gold, or a pla- 

 tinized platina plate, produces a more powerful voltaic cur- 

 rent than a platina plate does. On the 24th of last May, a 

 small platinized lead battery and a Grove's battery of the same 

 size, were exhibited before the Royal Irish Academy. The 

 power of the former was obviously superior to that of the 

 latter. By using double leads and single zincs instead of 

 double zincs and single leads, the power of the battery appears 

 to be increased. When the lead plates have been used for a 

 long time, they require to be newly gilded or platinized. After 

 being used they should be rinsed in water, and dipped into a 

 weak solution of chloride of gold or platina. 



