Page:Waylaid by Wireless - Balmer - 1909.djvu/191

Rh of the Polporru land station. At the lower end of those wires—both upon the ship and upon shore—is a powerful sending apparatus which discharges a very powerful current into the wires, when the key is pressed, which is felt by every similar set of wires anywhere within a circle of some hundreds of miles. The effective radius for a ship's 'wireless' installation is seldom more than two or three hundred miles. A shore station sometimes sends much further than that, according to conditions. But at Polporru to-day the police are counting upon the ordinary communication radius of a couple of hundred miles. As the 'wireless' waves will spread out from Polporru in a ring in every direction, they know they must find the Bahia well within the circle of three hundred miles. They need not know where, exactly. Whereever she is, they can call and communicate with her as confidently as though they had strung a wire to her and were telegraphing over that.

"Indeed, the chief difference between 'wireless' communication and that with wires to 169