Science: Beams

Newspaper readers pictured a narrow, shooting band, like the track of a searchlight, flashing from England and wagging over Canada until it found its mark. That was essentially the right picture, except that where a searchlight beam starts out intensely bright and soon dwindles palely, the beam in question remained almost as powerful 3,000 miles from its starting point; and except that it was, of course, an invisible beam, a shaft of radio waves.

The picture was conjured by an announcement in Britain that the royal and imperial Post Office had certificated Messere Guglielmo Marconi’s latest “directive” system of transoceanic short-wave radio communication for use between Britain and Canada. Experiments of the last three months had proved the efficacy of Marconi devices which reflect and concentrate the waves issuing from a transmitting aerial. The chief advantages of the shaft of waves thus obtained are its relative secrecy, and its power in adverse weather conditions. Instead of rushing out through the air in all directions, the directed waves stay in a column some 150 miles in width at its widest. Further secrecy, and the highly important element of speed, had been obtained by adoption of the multiple impulse—sending several messages simultaneously on one wave by, so to speak, filing niches for them in the wave’s troughs. Post Office officials had stipulated that the best speed of transmission known commercially—about 500 letters per minute—must be equaled for the certificate. The Marconi Co. produced an average speed of 600 letters per minute; a maximum of 1,250 letters; predicted extension of its service to Africa, to Australia.