124 Prof. J. C. Poggendorff on the Induction Apparatus 



A piece of paper saturated with nitrate of silver, percliloride 

 of platinum or percliloride of gold, is coloured brown under- 

 neath the positive stream of sparks. Witli perchloride of gold 

 and perchloride of platinum the sparks themselves have a brown 

 colour. 



Underneath them the paper begins to smoke, it soon dries, 

 and now a hole is burned through it, which, glimmering like a 

 fusee at tlie edges, rapidly increases in size. Brown filaments 

 rise from the paper, attach themselves to the wire, and form 

 a kind of beard around the same. Underneath the negative 

 stream of sparks these phajnomena do not manifest themselves, 

 but a dark spot is there formed, which evidently consists of 

 reduced metal. 



The eflfects of the induction current are now described. The 

 reason why that current is only active which is produced by 

 breaking the inducing current, and why the otherj generated by 

 closing the same, has no action and does not possess the re- 

 quisite tension to break through so thin a stratum of air, is 

 simply to be sought in the fact, that by closing the current a 

 complete conducting circuit is formed, which, like all continuous 

 metallic circuits surrounding the induction coil internally or 

 externally, is unfavourable to the development and the duration 

 of the current induced therein. 



Good conducting liquids, like those of a galvanic circuit, are 

 in this respect not different from metals. Of this it is easy 

 to arrive at a conviction if the primary coil possesses two wires. 

 When the galvanic current is sent through one of these wires 

 .only, and the other is connected with a pair of metallic plates, the 

 development of sparks by the induction coil is immediately sus- 

 pended when these plates are immersed in dilute sulphuric 

 acid*. 



Under ordinary circumstances, when the current is broken, 

 the destruction of the closed circuit itself removes this im- 

 pediment, and nothing impedes the full development of the 

 current in the induction coil, consequent upon this act, except 

 what may be termed an accumulation of electricity at the ends of 

 the interrupted inducing current, as well as a similar accumula- 



* For the same reason a former experiment of mine failed. I there at- 

 tempted to generate a strong induction current by continually reversing 

 the magnetization of the soft iron core of the apparatus. It is easy to 

 produce this reversion tcitkoiit interruption. For this purpose it is only 

 necessary to keep one wire of the jirimaiy coil continually connected with 

 one galvanic element, and to connect the other, in opposite direction, with 

 a battery consisting of two such elements, and continually interrupted by a 

 Neef's hammer. This combination, however, did not produce the intended 

 result, because within the induction coil a circuit closed by a good con- 

 ducting liquid was always present. 



