VOLTAIC ELECTRICITY. 



241 



resistance, large cells, or several cells in multiple arc are 

 preferable. 



(a.) A battery of liigli resistance was formerly called an intensity 

 battery, while a battery of low resistance was called a quantity 

 battery. 



FIG. 184. 



381, Daniell's Battery. In the cell of Daniell's 

 battery (Fig. 185), the zinc plate is in the form of a cleft, 

 hollow cylinder. Within this cylinder is a porous cup; 

 within the porous cup is the copper cylindrical plate. The 

 liquid used is dilute sulphuric acid, but the acid within 

 the porous cup has as much 

 copper sulphate as it can dis- 

 solve, i. e. y it is saturated. For 

 the purpose of keeping this 

 acid saturated, crystals of cop- 

 per sulphate are suspended in 

 it near the surface, by means 

 of a copper wire basket or per- 

 forated earthenware cup. The 

 effect of this is to cause the 

 hydrogen to re-enter into 

 chemical combination before it 

 reaches the copper plate. Copper, instead of hydrogen, is 



FIG. 185. 



