Lemox. — On Duplex Telegraphy. 401 



My experiment with the two induction coils was as shown in Plate XXVII. 

 The two vacuum spheres, IJ inch in diameter, had platinum wire points {x) 

 at a distance of about half an inch above and below a platinum wire («), that 

 went right through from one side of each sphere to the other at right angles, 

 and also axial, as shown in diagram. The sparking poles A and C of the two 

 induction coils were joined to "F and E of the spheres, and the receiving poles 

 B and D of the coils joined to H and G ; thus the spark from No. 1 coil 

 would pass from A to F, then through the No. 1 sphere, then across the 

 vacuum tube, then on to G by way of z, and back to its own receiving pole B. 

 The spark from coil No. 2 would pass from C to E, then spark through the 

 No. 2 sphere, then through the vacuum tube, then on to H by way of z, and 

 back to its own receiving pole D ; thus, by these means, the phenomena of two 

 currents of electricity passing through the same space and in opposite directions 

 were rendered visible. 



The vacuum tube, in addition to the spiral tube passing through it, was in 

 globular form at each end, when the spark passed out of the sphere from coil No. 

 1 (its spark being passed though by itself first, and then No. 2 treated in the 

 same manner) : in the end of the vacuum tube, next the coil No. 1, the light in 

 it assumed a striped appearance, and, after passing through the tube, assumed 

 in the other end a glowing-like appearance, like teased-out cotton wool. The 

 spark from No. 2 coil, treated in the same manner, showed just the same 

 results in the contrary direction. When only one coil was in operation, the 

 light in the spiral tube was very luminous; but when both were in operation 

 at one and the same time, this light was rendered doubly so, thus proving 

 there was double the quantity of light in the tube when both currents were on 

 at the same time. This was most distinctly visible. 



Another experiment I tried was connecting a Morse key between the one 

 pole of the battery and the make and break of each coil : — When the key was 

 depressed the flashes of flame could be distinctly seen discharging at either end 

 of the vacuum, the signal coming from No. 2 could be plainly seen and read off 

 at the H end of the tube in the cotton wool form described, whilst the striped 

 appearance of the spark in the H end (the same end) of the tube from coil 

 No. 1 could also be seen there. Previous to the last experiment above 

 referred to, I made another by detaching the two receiving poles from G and 

 H, and joining them together, so that the spark that passed from No. 1 coil 

 before it could get back to its own receiving pole was forced to travel through 

 the secondary wire of coil No. 2. Coil No. 2 had to perform the same 

 operation as No. 1 before its spark could reach its own receiving pole. 

 When the connections were joined up this way, at intervals, a spark would 

 pass in either coil direct from its own sparking pole to its own receiving 

 pole, and this whilst the light was in the vacuum tube. It would appear, from 



c2 



