Besides, there 's no mystery about land-lines. Why, you 've only got to stick up a lot o' posts with insulators screwed to 'em, fix wires to the insulators, clap on an electric battery and a telegraph instrument, and fire away."
"Robin, what are insulators?" asked Madge, with a puzzled look.
"Madge," replied Robin, with a self-satisfied expression on his pert face, "this is the three-hundred-thousandth time I have explained that to you."
"Explain it the three-hundred-thousand-and-first time, then, dear Robin, and perhaps I'll take it in."
"Well," began Robin, with a hypocritical sigh of despair, "you must know that everything in nature is more or less a conductor of electricity, but some things conduct it so well—such as copper and iron—that they are called conductors, and some things—such as glass and earthenware—conduct it so very badly that they scarcely conduct it at all, and are called non-conductors. D'ee see?"
"Oh yes, I see, Robin; so does a bat, but he doesn't see well. However, go on."
"Well, if I were to run my wire through the posts that support it, my electricity would escape down these posts into the earth, especially if the posts were wet with rain, for water is a good con-
