"It is, indeed, a wireless installation, sir," said Marbeau, "or, at least, part of one. Most of the instruments of transmission are here, but there are no recording instruments. In other words, wireless messages might be sent from here, but none could be received—unless this is a recorder of some sort," and he pointed to a small instrument of clock-like appearance which stood on the table.
"No," said Crochard; "that is not a recorder—that is the sender."
"The sender?" repeated Marbeau.
"Yes. You have noticed there is no key?"
"Yes, and I do not understand its absence."
"This device takes the place of it—it was by means of this that the spaced signals were sent. Listen."
He bent above the clock, and the others heard a sound as of a strong spring being wound. Then he stood erect: there were two sharp ticks; then a long white snap of electricity; two ticks and another snap; two ticks and another snap....
"Yes, that is the signal!" cried Marbeau, and bent again above the mechanism. In a moment he understood.
Before the clock-face was a single long hand, a second-hand, terminating in a thin, spring-like strip of platinum. The circumference of the face was divided into sixty spaces, and at every third space was a slender copper pin, which the end of the second-hand touched in passing. Two wires, one connected with the second-hand, the other presumably with the copper pins, ran from the clock down to the heavy batteries on the floor. Every three seconds the circuit was automatically closed, and a long flash sent along the conducting wire out into the air. Marbeau stood listening for a moment longer, then loosened one of the wires. The signals stopped.
"Now let us see the aerial," he said, and led the way outside.