2J ELECTRIC LIGHTING. 



out of one of those residues which are taken from the retorts 

 of gasworks after the distillation. This form of carbon is 

 very hard, very compact, and relatively a good conductor. 

 The communicating wires are joined to these electrodes by 

 two brass clamps, the one of large size covering the upper 

 part of the carbon and pressed against its surfaces, the other 

 provided with a binding screw aperture for holding the nega- 



tive wire is applied to a slip of copper riveted to the zinc 

 cylinder. The arrangement of a cell of this battery is shown 

 in Fig. 4. 



This arrangement may be reversed, and as regards the 

 constancy of the battery there would be a gain in doing so, 

 for, as I have shown, the effects of polarization are less in 

 proportion as the negative electrode is larger ; but as the 

 electric light requires a great consumption of zinc, this sub- 

 stance must be placed in the cell in sufficiently large quantity, 



