338 Intelligence and Miscellaneous Articles, 



one arc, and that the other resistance in the circuit, in which no 

 light is produced, has remained constant throughout. 



If we had a material infinitely conductiug, of infinite strength, 

 and with a melting point at least as high as that of carbon, then 

 surely the division of the light would be perfectly economical up to 

 any limit, inasmuch as we might then use linear electrodes. 



In practice we can only try to approach this limit. Up to the 

 present time there appears to be no better material for electrodes 

 than carbon, either natural or artificial. But this is no reason why 

 an effort should not be made to try to find a material for electrodes 

 more accommodating to the division of the electric light than even 

 carbon. The above, limited strength, limited electric conductivity, 

 and limited melting-point of the material of electrodes, constitute 

 only one of the difficulties which stand in the way of an unlimited 

 economical division of the electric light. 



A second cause is, for instance, the fact that in each arc an E.M. 

 F. is established opposite to the original E.M.F. and by no means 

 to be neglected against it. This secondary E.M.F. established in 

 each arc appears to be a function of the current which passes the 

 arc, most likely proportional to that current. Hence, if for a given 

 current passing one arc this secondary E.M.F. be e, then the same 

 current through n arcs, successively connected, would produce an 

 E.M.F. equal to n e. This secondary E.M.F. n e is to be subtracted 

 from the original E.M.F. ; and, internal resistance of the original 

 E.M.F. plus resistance of leading wires having remained constant, 

 we necessarily have to decrease the total resistance of the n arcs 

 in order to work with the same current as before. This merely 

 means a decrease of the total length of the n arcs, or, which is the 

 same, an increase of internal light or decrease of the measured or 

 external light. A parallel connexion of the n arcs with reference 

 to the poles of the given original E.M.F. would certainly produce 

 only one secondary E.M.F. instead of n ; and for this reason it 

 might be better to use the parallel circuit for the division of the 

 electric light. But there are other very important objections to 

 this solution. In the first place, as can be easily shown, the varia- 

 tion of one arc has a far greater influence on the variation of the 

 others in parallel, than in successive circuit. Further the length 

 of each arc must be made very much smaller in parallel circuit 

 than in consecutive circuit. 



Another reason against an unlimited economical division of the 

 electric light is constituted by the practical necessity that lamps, 

 of whatever construction they may be, have a resistance inherent 

 to their nature in addition to the resistance of the arc. For in- 

 stance, in an ordinary lamp with an electromagnet, the resistance 

 of the lamp consists of the resistance of the electromagnet plus the 

 resistance of the two electrodes when metallically closed. This 

 resistance, although small, is by no means nil, and cannot be neg- 

 lected against the resistance of the arc, especially when strong 

 currents are used. In other words, when producing the electric 

 light in n points instead of one point, we are unable to practi- 



