62 FRAGMENTS OF SCIENCE. 



force with which these atoms lock themselves together, 

 we have the means of tearing them asunder, and the 

 agent by which we accomplish this may here receive a 

 few moments' attention. 



Into a vessel containing acidulated water I dip 

 two strips of metal, the one being zinc and the other 

 platinum, not permitting them to touch each other 

 in the liquid. I connect the two upper ends of the 

 strips by a piece of copper wire. The wire is now the 

 channel of what, for want of a better name, we call an 

 ' electric current.' What the inner change of the wire 

 is we do not know, but we do know that a change has 

 occurred, by the external effects produced by the wire. 

 Let me show you one or two of these effects. Before 

 you is a series of ten vessels, each with its pair of 

 metals, and I wish to get the added force of all ten. 

 The arrangement is called a voltaic battery. I plunge 

 a piece of copper wire among these iron filings; they 

 refuse to cling to it. I employ the selfsame wire to con- 

 nect the two ends of the battery, and subject it to the 

 same test. The iron filings now crowd round the wire and 

 cling to it. I interrupt the current, and the filings imme- 

 diately fall; the power of attraction continues only so 

 long as the wire connects the two ends of the battery. 



Here is a piece of similar wire, overspun with cot- 

 ton, to prevent the contact of its various parts, and 

 formed into a coil. I make the coil part of the wire 

 which connects the two ends of the voltaic battery. 

 By the attractive force with which it has become sud- 

 denly endowed, it now empties this tool-box of its iron 

 nails. I twist a covered copper wire round this com- 

 mon poker; connecting the wire with the two ends of 

 the voltaic battery, the poker is instantly transformed 

 into a strong magnet. Two flat spirals are here sus- 

 pended facing each other, about six inches apart. 



