388 FRAGMENTS OF SCIENCE. 
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 cop- 
per 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 immediately 
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 cotton, 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 suddenly endowed, it now 
empties this tool-box of its iron nails. I twist a covered 
copper wire round this common poker; connecting the 
wire with the^tvvo ends of the voltaic battery, the poker is 
instantly transformed into a strong magnet. Two flat 
spirals here are suspended facing each other, about six inches 
apart. Sending a current through both spirals, they clash 
suddenly together; reversing what is called the direction 
of the current in one of the spirals, they fly asunder. All 
these effects are due to the power which we name an elec- 
tric current, and which we figure as flowing through the 
wire when the voltaic circuit is complete. 
By the same agent we tear asunder the locked atoms of 
a chemical compound. Into this small cell, containing 
water, dip two thin wires. A magnified image of the cell 
is thrown upon the screen before you, and you see plainly 
the images of the wires. From a* small battery I send au 
