Signalling beyond a third of a mile or so was a daring idea in 1892. The demonstrated range so far was only a few hundred yards. But contemporaries suspected that much could be done yet with wireless electricity. Their inferential models of current in the air were growing in sophistication. William Crookes, the physicist, aware of the work of Heinrich Hertz and Oliver Lodge, and having himself worked a bit with David Hughes, imagined electrical intelligence vibrating in the ether in all directions, or refracted in directional ‘sheafs of rays’ through pitch lenses, in wavelengths of thousands of miles down to a few feet. Received signals ought to be made louder by reflection, he thought. Signals fade, he observed, ‘according to the law of inverse squares.’ He was aware that receivers could be made to ‘respond to wavelengths between certain defined limits and be silent to all others,’ by ‘turning a screw or altering the length of a wire.’ In this he was ahead of where Marconi was ten years later. Signals restricted to as little band space as possible, added, would be difficult to find, and therefore tantamount to private.
William Crookes, “Some Possibilities of Electricity,” Fortnightly Review, February 1, 1892, pp. 174-6.
Picture: Assembling cathode-ray ‘Crookes Tubes’, in H. Snowden Ward, “Marvels of the New Light: Notes on the Röntgen Rays. The Windsor Magazine, vol. 3 (Jan 1896):372-84.