You perceive that we can take about this
heating agent wherever we like, and deal with it as we please, limiting it
in any way. I am obliged to deal carefully with it; but even that
circumstance will have an interest for you in watching the experiment.
Contact is now made. The electric current, when compressed into thin
conducting-wires offering resistance, evolves heat to a large extent; and
this is the power by which we work. You see the intense glow immediately
imparted to the wire; and if I applied the heat continuously, the effect
of the current would be to melt the wire. As soon as the contact is
broken, the wire resumes its former appearance; and now that we make
contact again, you perceive the glow as before. [The experiment was
repeated several times in rapid succession.] You can see a line of light,
though you can scarcely perceive the wire; and now that it has melted with
the great heat, if you examine it, you will perceive that it is indeed a
set of irregularities from end to end--a set of little spheres, which are
strung upon an axis of platinum running through it. It is that wire which
Mr. Grove described as being produced at the moment when fusion of the
whole mass is commencing. In the same manner, if I take a tolerably thick
piece of platinum, and subject it to the heat that can be produced by this
battery, you will see the brilliancy of the effect produced.
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