“But,” continued Robin impressively, “if I fix little lumps of glass with a hole in them to the posts, and fix my wires to these, Electricity cannot bolt, because the glass lumps are non-conductors, and won’t let him pass.”
“How good of them!” said Madge.
“Yes, isn’t it? So, you see,” continued Robin, “the glass lumps are insulators, for they cut the electricity off 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.