324 Intelligence and Miscellaneous Articles. 



The passage of the currents in a Ruhmkorff's coil deserves 

 special attention. 



The contact-breaker being suppressed, Nollet's apparatus pro- 

 duces in the induced wire effects of tension which are so weak 

 that a spark of J millimetre in length is with difficulty obtained. 

 But on introducing into the circuit the dialyzing voltameter, the 

 aspect of the experiment is changed. A spark, several centimetres 

 in length, is obtained ; the induced current passes in M. E. Bec- 

 querel's tubes, as well as in those of Geissler, so long as one set 

 of currents retains an action which is independent of the other 

 series. The poles in the tubes are well marked. But if the con- 

 ductivity of the dialyzer be increased, all the currents pass with 

 their normal properties, and act simultaneously on the coils. 



It would appear to follow from these facts, that the introduc- 

 tion of the dialyzer into the circuit gives rise to the extra currents 

 of either one series or the other, or to both, at the will of the 

 operator. 



We may, in any case, say that the dialyzer applied to Ruhm- 

 korff's coil acts as perfectly as the best contact-breaker. It must 

 be added that, if it is not desired to absorb one series of the 

 currents, all liquids which are good conductors are equally suit- 

 able. 



In order to obtain an approximate value for the effects of the 

 dialyzing voltameter, we introduced into the circuit a Bunsen's 

 element, which, by means of the commutator, could act first in the 

 direction of the currents of the machine, and afterwards in opposition 

 to them. 



In the first case, a sine-compass indicated a deflection of 31 

 degrees, the sine of which =5"5 ; in the second, a deflection of 

 20 degrees, the sine of which is 3-42. From this we get the 

 number 5 as the ratio between the electromotive force of the 

 series of currents and that of a Bunsen's element. 



We have seen above that the electromotive force of the magneto- 

 electrical machine, with a thick wire, represented that of a battery 

 of 22 sulphate- of-copper elements, the effect of which, according 

 to M. Becquerel, is equal to that of 13| Bunsen's elements. Erom 

 this, the useful effect obtained by means of the dialyzer would be 

 _s^_. of that which could be expected from the adjustment of the 

 currents. 



New experiments which are in progress may perhaps modify 

 this conclusion a little. We may, however, say that, whenever 

 the operator is desirous of arranging an economical motor at the 

 risk of losing the useful effect of magneto -electrical machines, it 

 will be to his interest to dispense with the adjustment of currents, 

 requiring as this does a commutator, the use of which is attended 

 with inconvenience. — Comptes Hendus, Dec. 9, 1867. 



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