Intelligence and Miscellaneous Articles, 405 



they give off, the ear recognizes a distinct tone conformable with that 

 of the vibrating plate. 



At the same time that it regulates the sparks, this new inter- 

 ruptor, when applied to the ordinary machines in use, is capable of in- 

 creasing their power to a certain extent. It generally acts so as to 

 •render the effects proportionate to the intensities of the current dis- 

 tributed, whence it follows that it is particularly in the employment 

 of strong currents that it presents a marked advantage over the in- 

 terruptors with solid points of contact. 



It is even imprudent with a single machine of ordinary dimen- 

 sions, to attempt to force the intensity of the inducing current 

 beyond a certain limit, for this will infallibly cause the induced 

 coil to burst internally. But by combining several machines, the 

 sum of the tensions being divided between the various elements of 

 this kind of battery, we may direct upon the whole the action of a 

 number of couples proportional to that of the machines, which in- 

 creases in the same proportion the distance passed over by the spark 

 between the two extremities of the induced series. This system of 

 combination applies without difficulty to the excellent machines con- 

 structed by M. Ruhmkorff, provided they are only combined in pairs. 



The hammers are suppressed and replaced by permanent conduct- 

 ors, the two inducing wires are united one after the other, and the 

 interruptor, accom])anied by the condenser of the extra- current, is 

 introduced into the circuit. By this precaution each machine must 

 retain its discharge wires at a normal distance ; both also retain 

 their commutators, which serve respectively to direct the two parts of 

 the current in such directions that tensions of opposite signs may 

 accumulate at the internal extremities of the induced wires ; and 

 lastly, these being put in communication, the external ends which 

 remain free, become the two poles of the system, and furnish sparks 

 at a distance of 30 to 35 millimetres. 



When it is desired to place more than two machines under the 

 conduct of the mercurial interruptor, it becomes necessary to isolate 

 the additional machines with particular care. In fact, in comparison 

 with the very strong tensions which are manifested in the induced 

 wire in the neighbourhood of the extremities, the inducing wire 

 which penetrates the axis of the coils must be regarded as an 

 inert conductor, and if this conductor approaches the induced coils 

 at points more or less distant from those in which the tensions are 

 null, it presents a complete course for the discharge. It is therefore 

 important to effect an absolute isolation between the inducing wire 

 and the interior of the induced coil in the additional machines, and 

 this isolation is effected by slipping a glass tube into the annular 

 space which separates the two concentric coils. As soon as this 

 condition was fulfilled by the care of M. Ruhmkorff, four combined 

 machines gave the effects of tension, which might have been ex- 

 pected, and the sparks darted across an interval of 7 or 8 centi- 

 metres. — Comptes Rendus, July 7, 1856, p. 44. 



