30 



DESCRIPTION OF GALVANIC BATTERIES. 



We have just stated that a battery composed of zinc and platinum 

 will be more powerful than one composed of zinc and copper, so far 

 as regards their negative and positive tendencies ; but so much does 

 the conducting power of the negative metal effect the practical use- 

 fulness of a battery, that notwithstanding the fact that platinum is 

 much more negative than copper, there is so much of the effective 

 electricity expended in overcoming the resistance which the inferior 

 conductivity of the platinum offers to the progress of the current, 

 that a battery of zinc and copper proves to be a more effective and 

 useful battery for electro-metallurgy than one onade of zinc and 

 platinum. Hence also the reason that iron and copper, or iron and 

 any other metal, make but an indifferent battery iron being a bad 

 conductor; while lead, which will be seen in the table, stands 

 lowest in this property, is therefore unfit for batteries. 



In fitting up a voltaic arrangement with a negative metal that is 

 not a good conductor, such as platinum, the closer it is placed to the 

 exciting liquid, in connection with another metal that is a good 

 conductor, the better; because the current obtained will be the 

 more effectual. 



Babington's Battery. If we look back to the description given 

 of the voltaic pile (page 1), and the improvement made upon it by 

 Cruikshanks, we perceive the relation they bear to the pieces of 

 copper and zinc mentioned in page 24 ; but the relation is more 

 apparent in Babington's improvement upon Cruikshanks' battery. 

 When working with this battery, it was found that the energy of 

 the battery did not depend, as was supposed, upon the extent of 

 surface of the zinc and copper which were in contact, but upon the 

 extent of surface of these metals in contact with the liquid with 

 which the battery was excited ; and that it was sufficient if the zinc 

 and copper touched each other in a single point ; provided 



that the plates were 

 plunged into the li- 

 quid, and that the 

 copper plate should 

 be exactly opposite 

 to a zinc plate in 

 the same cell, a 

 space being be- 

 tween them. Hence, 

 instead of soldering 

 the zinc and copper 

 together, as Mr. 

 Cruikshanks did, it was enough to effect a communication by turning 

 over a portion of the copper plate at the top, and soldering it to the 

 upper extremity of the zinc. Thus c, the copper, is bent over to 



