WIRELESS TELEPHONY FESSENDEN. 163 



possessed by the Hertz waves of passing through fog and mate- 

 rial obstacles made them particularly suitable for use for electric 

 signaling. 



Prof. Elihu Thomson, in a lecture delivered at Lynn, Mass., on 

 " Alternating currents and electric waves," in 1889, suggested 

 this use. 



Sir William Crookes in the Fortnightly Eeview for February, 1892, 

 discussed the matter in some detail. I quote his statement in full, 

 as it shows what a clear conception he had of the possibilities and 

 obstacles to be overcome : 



Here is unfolded to us a new and astonishing world, one which it is hard to 

 conceive should contain no possibilities of transmitting and receiving intelligence. 



Rays of light will not pierce through a wall, nor, as we know only too well, 

 through a London fog. But the electrical vibrations of a yard or more in wave 

 length of which I have spoken will easily pierce such medium, which to them 

 will be transparent. Here, then, is revealed the bewildering possibility of 

 telegraphy without wires, posts, cables, or any of our present costly appliances. 

 Granted a few reasonable postulates, the whole thing comes well within the 

 realms of possible fulfillment. At the present time experimentalists are able to 

 generate electrical waves of any desired wave length from a few feet upward, 

 and to keep up a succession of such waves radiating into space in all directions. 

 It is possible, too, with some of these rays, if not with all, to refract them 

 through suitably shaped bodies acting as lenses, and so direct a sheaf of rays 

 in any given direction ; enormous lens-shaped masses of pitch and similar bodies 

 have been used for this purpose. Also an experimentalist at a distance can 

 receive some, if not all, of these I'ays on a properly constituted instrument, and 

 by concerted signals messages in the Morse code can thus pass from one operator 

 to another. What, therefore, remains to be discovered is : Firstly, simpler and 

 more certain means of generating electrical rays of any desired wave length, 

 from the shortest, say of a few feet in length, which will easily pass through 

 buildings and fogs, to those long waves whose lengths are measured by tens, 

 hundreds, and thousands of miles ; secondly, more delicate receivers, which will 

 respond to wave lengths between certain defined limits and be silent to all 

 others; thirdly, means of darting the sheaf of rays in any desired direction, 

 whether by lenses or reflectors, by the help of which the sensitiveness of the 

 receiver (apparently the most difllcult of the problems to be solved) would not 

 need to be so delicate as when the rays to be picked up are simply radiating into 

 space in all directions and fading away according to the law of inverse squares. 



I assume here that the progress of discovery would give instruments capable 

 of adjustment by turning a screw or altering the length of a wire, so as to 

 become receptive of wave lengths of any preconcerted length. Thus, when 

 adjusted to 50 yards, the transmitter might emit, and the receiver respond to, 

 rays varying between 45 to 55 yards and be silent to all others. Considering 

 that there would be the whole range of waves to choose from, varying from 

 a few feet to several thousand miles, there would be sufficient secrecy, for 

 curiosity the most inveterate would surely recoil from the task of passing in 

 review all the millions of possible wave lengths on the remote chance of ulti- 

 mately hitting on the particular wave length employed by his friends whose 

 correspondence he wished to tap. By '• coding " the message even this remote 

 chance of surreptitious straying could be obviated. 



