VOLTAIC BATTERIES. 



53 



operator must be careful that the silver in no place touches the 

 zinc. The arrangement thus immersed will be found to produce 

 no effect on the liquid until a communication is made between 

 the metals, when a violent evolution of hydrogen gas takes 

 place, and an active voltaic battery is obtained. If, however, 

 the zinc be imperfectly amalgamated, or from want of care in 

 the immersion of the arrangement, the silver plate has any 

 portion of its surface in connection with the zinc, an action is 

 apparent. In the former case, it depends on the want of 

 protection afforded by the coating of mercury to the zinc, and 

 may be easily obviated by fresh amalgamation ; in the latter it 

 is still more easily remedied by examination, and the separation 

 of the metals wherever they may be in contact. This form of 

 battery is the one usually sold for medical purposes by the 

 publishers of this work. 



For intensity effects, Smee's Battery may be arranged as an 

 ordinary Wollaston with advantage, as shown in Fig. 10. Ten or 



Fig. 10. 



1 2 form an elegant battery, sufficiently powerful for all medical 

 purposes. This arrangement is a general favourite, and is 

 probably more extensively used than all the other forms put 

 together. It is simple in construction, exceedingly manageable, 

 and elegant in its appearance ; and although it is not so con- 

 stant as that invented by Professor Daniell, nor possessed of the 

 intense energy of Professor Grove's, it has the great advantage 

 of being almost instantaneously set in action, and as quickly 

 cleaned and put aside. Hence its great utility for medical pur- 



