from the earth as an island
is, or, at all events, appears to be, cut off from it by water; and
Mister Electricity _must_ go along the wires and do what I tell him. Of
course, you know, I must make my electricity first in a battery, which,
as I have often and often told you, is a trough containing a mixture of
acid and water, with plates or slices of zinc and copper in it, placed
one after the other, but not touching each other. Now, if I fix a piece
of wire to my first copper slice or plate, and the other end of it to my
last zinc slice or plate, immediately electricity will begin to be made,
and will fly from the copper to the zinc, and so round and round until
the plates are worn out or the wire broken. D'ee see?"

"No, Robin, I don't see; I'm blinder than the blindest mole."

"Oh, Madge, what a wonderful mind you must have!" said Robin, laughing.
"It is _so_ simple."

"Of course," said Madge, "I understand what you mean by troughs and
plates and all that, but what I want to know is _why_ that arrangement
is necessary. Why would it not do just as well to tempt electricity out
of its hiding-hole with plates or slices of cheese and bread, placed one
after the other in a trough filled with a mixture of glue and melted
butter?"

"What stuff you do talk, Madge! As well might you ask why it would not
do to make a plum-pudding out of nutmegs and coal-tar. There are some
things that no fellow can understand, and of course I don't know
_everything_!"

The astounding modesty of this latter remark seemed to have furnished
Madge with food for reflection, for she did not reply to it. After a
few minutes' walk the amateur electricians reached the scene of their
intended game--a sequestered dell in a plantation, through which brawled
a rather turbulent stream. At one part, where a willow overhung the
water, there was a deep broad pool. The stream entered the pool with a
headlong plunge, and issued from it with a riotous upheaval of wavelets
and foam among jagged rocks, as if rejoicing in, and rather boastful
about, the previous leap.

The game was extremely simple. The pool was to be the German Ocean, and
a piece of stout cord was to serve as a submarine cable.

The boy and girl were well-matched playmates, for Madge was ignorant and
receptive--in reference to science,--Robin learned and communicative,
while both were intensely earnest.

"Now, this is the battery," said Robin, when he had dug a deep hole
close t