182 



Description of a Carbon Voltaic Battery. 



this operation, the inner cells may be removed from the outer, 

 and allowed to stand in some convenient vessel until wanted for 

 use, so that the intermixing of the acids, which always hap- 

 pens, more or less, in twenty four hours, is avoided. 



The plumbago here employed, is the artificial mixture made at 

 the crucible works, and crowded into moulds of the proper shape, 

 and baked.* Only in a few instances have I found a cylinder 

 fail from the action of the nitric acid. Having failed to pro- 

 cure readily a sufficient quantity of natural plumbago, I was 

 induced to employ the present material, which, although inferior 

 in the energy of the results to the native mineral, is still very 

 good. The difficulty in procuring suitable cylinders of native 

 plumbago, arises not from the want of an abundance of the ma- 

 terial, but from the occurrence of numerous natural joints, even 

 in that which seems externally quite sound, which cause them 

 to fall to pieces under the saw. 



The mode of connecting the plumbago with the zinc, suggest- 

 ed itself to me from the difficulty and expense of employing 

 mercury, and I find it in every way better. The brass screw 

 enters nearly two inches into the plumbago. Its neck passes 

 snugly through the wood of the frame F, and the head presents a 

 large surface to attach a connector from the next zinc. 



Fig. 2. 



Fig. 2 shows the mode of arrangement adopted for each group 

 of twelve members ; the frame F F supports both the zincs and 

 plumbagos, and by it they are removed from the cups j a con- 

 nector of copper passes from the screw of each plumbago to the 



* To be obtained of J. W. Ingall, Taunton, Mass. 



