194 



NATURE 



[December 7, 191 



experiment might possibly secure what is wanted. What, 

 however, is claimed is that, to far as I am aware, it is 

 the first suggested solution of the problem of distant 

 electric vision in which the difficulty of securing the re- 

 quired extreme rapidity and accuracy of motion of the parts 

 is got over by employing for these parts things of the 

 extreme tenuity and weightlessness of kathode rays. 

 Indof.d, apart from the revoivin>< armatures of the alter- 

 nators employed for synchronisation, which present no 

 ditHculty, there is no more material moving part in the 

 suggested apparatus than these almost immaterial streams 

 of negative electrons. Furthermore, as will be seen, only 

 four wires, or three wires and earth connections at each 

 end, arc required. 



In the diagrammatic illustration the transmitter is shown 

 on the left-hand side and the receiver on the right-hand 

 side. The transmitter consists of a Crookes tube A fitted 

 with a kathode B, which sends a kathode-ray discharge 

 through a small aperture in the anode C, the kathode rays 

 being produced by a battery or other source of continuous 

 electric current giving some 100,000 volts. D and E are 

 two electromagnets placed at right angles to one another. 



T R A N SM I TTE R. 



Similarly, in the transmitting apparatus, tli 

 rays fall on a screen J, the whole surface of v. 

 search out every tenth of a second under the ii 

 the magnets O and E. Further, it is to be rem 

 as the two magnets D and D' and the two magnets < 

 and E' are energised by the same currents, the move 

 of the two beams of kathode rays will b« ei 

 synchronous, and the kathode rays will always fall 

 two screens H and J on each corresponding 

 simultaneously. 



In the transmitter the screen J, which is gas-ti^K 

 formed of a number of small metallic cubes 

 one another, but presenting a clean metallic 

 kathode rays on the one side, and to -■ 

 vapour, say sodium vapour, on the ' 

 cubes which compose J are made of s' 

 rubidium, which is strongly active phototltitiritai! 

 readily discharging negative electricity under the infl.. 

 of light, while the receptacle K is filled with a gas 

 vapour, such as sodium vapour, which conducts ne£ 

 electricity more readily under the influence of light 

 in the dark. 



LINE w I RE. 



which, when energised by alternating current, will deflect 

 the kathode rays in a vertical and in a horizontal direction 

 respectively. 



The receiving apparatus consists similarly of a Crookes 

 tube A' fitted with a kathode B', which, in circumstances 

 to be further described, transmits kathode rays through an 

 aperture in the anode C. D' and E' are two electro- 

 magnets placed at right angles, similar to those in the 

 transmitter, the two magnets D and D', which control the 

 vertical motions of the kathode-ray beam, being energised 

 from the same alternating dynamo F, which has a fre- 

 quency, say, of ten complete alternations per second ; 

 while the other two magnets E and E', which control the 

 horizontal movements of the kathode-ray beam, are 

 energised by a second alternating dynamo G having a 

 frequency of, say, looo complete alternations per second. 



In the receiver H is a fluorescent screen, upon which, 

 under conditions to be further described, the kathode rays 

 impinge, and the whole surface of which they search out 

 every tenth of a second under the combined deflecting 

 influence of the two magnets D' and E', with the result 

 that under these conditions the screen fluoresces with what 

 appears to the eye as a uniform brilliancy. 



NO. 2197, VOL. 88] 



Parallel to the screen J is another screen of 11 

 gauze L, and the image to be transmitted of the obj 

 is projected by the lens M through the gauze screen 

 to the screen J through the vapour contained in K. 

 gauze screen L of the transmitter is connected tl 

 the line wire to a metallic plate O in the receiver» 

 which the kathode rays have to pass. There is, 

 a diaphragm P fitted with an aperture in such a 

 as, having regard to the inclined position of B', to 

 the kathode rays coming from the latter and prevent 

 from reaching the screen H unless they are slightly 

 from the plate O, when they are able to pass throu 

 aperture. 



The whole apparatus is designed to functia 

 follows : — 



Assume a uniform beam of kathode rays to be 

 in the Crookes tubes A and A', and the magnets D 

 and D' and E' to be energised with alternating cur 

 mentioned. Assume, further, that the image that is 

 to be transmitted is strongly projected through the_ 

 through the gauze screen L on to the screen J. 

 the kathode rays in A oscillate and search out the «:? 

 of J, they will impart a negative charge in turn to r 



