“Then it isn’t a cir—” Lee began.
“Yes, it is! Think, boy! This old earth of ours is a mighty good electric conductor—”
“Of course!” Lee was crestfallen that he hadn’t thought of that. “I’ve grounded wires myself, and made the circuit.”
“All right then. We’ve got our wire going to Birmingham, grounded at the Birmingham station, and the earth acting as a return for our current. Now we’ll say this circuit is fixed around some instruments on my table, and fixed around the same sort of instruments on the table in Birmingham. Well, when I start tapping my telegraph key—making and breaking the circuit—won’t this current be stopped and started at Birmingham just like it is here? Huh?”
“Yes—an instrument on the same circuit.” Lee cocked his head sidewise in deep thought. “It just naturally would be.”
“Well, son, that’s telegraphy!”
“Telegraphy! Great jumping catfish! Is that all there is to it?”
“Er-r, not exactly,” said Akerly dryly. “There’s the relay, or local battery circuit, the electromagnet sounder, special stuff and duplex work, signals, the code to be learned.” The dispatcher paused a moment in his recital, pulled a battered book out of a drawer, opened it at a page full of queer marks, and added, “Here’s the code.”
Lee bent over the page. “I see,” he said, then added with a wry grin, “or rather I don’t see! How do you hitch all those little signs up so that they mean something on an instrument?”
“All right—it’s like this. I’ll tap the telegraph key for a tenth of a second. That means I’ve let the current flow for a tenth of a second. We call that a 'dot.’ A three-tenths of a second tap makes the 'dash.’ Put 'dot,’ 'dash,’ 'dot’ together in all sorts of combinations, and you’ve got the code. When the fellow at the other end of the line knows the code, he can understand what you’re tapping to him.”