Mark Twain: A Connecticut Yankee in King Arthur's Court

THE TALE OF THE LOST LAND CHAPTER 42: WAR! (continued)

"The fences are fastened to heavy oaken posts only three feet apart, and these posts are sunk five feet in the ground."

"That is good and strong."

"Yes. The wires have no ground-connection outside of the cave. They go out from the positive brush of the dynamo; there is a ground-connection through the negative brush; the other ends of the wire return to the cave, and each is grounded independently."

"No, no, that won't do!"

"Why?"

"It's too expensive--uses up force for nothing. You don't want any ground-connection except the one through the negative brush. The other end of every wire must be brought back into the cave and fastened independently, and without any ground-connection. Now, then, observe the economy of it. A cavalry charge hurls itself against the fence; you are using no power, you are spending no money, for there is only one ground-connection till those horses come against the wire; the moment they touch it they form a connection with the negative brush through the ground, and drop dead. Don't you see?--you are using no energy until it is needed; your lightning is there, and ready, like the load in a gun; but it isn't costing you a cent till you touch it off. Oh, yes, the single ground-connection--"

"Of course! I don't know how I overlooked that. It's not only cheaper, but it's more effectual than the other way, for if wires break or get tangled, no harm is done."

"No, especially if we have a tell-tale in the cave and disconnect the broken wire. Well, go on. The gatlings?"

"Yes--that's arranged. In the center of the inner circle, on a spacious platform six feet high, I've grouped a battery of thirteen gatling guns, and provided plenty of ammunition."

"That's it. They command every approach, and when the Church's knights arrive, there's going to be music. The brow of the precipice over the cave--"