112 Prof. E. Edlund's Investigation of the Electric Light. 



That D should be independent of the intensity, at first sight 

 seems unexpected ; closer consideration shows, however, that 

 this entirely agrees with other properties of the voltaic current 

 which are connected with it. The work which the current exerts 

 in disintegrating the points of the poles is measured by the di- 

 minution in the total heat developed by the current which re- 

 sults from the electromotive force I) caused by the disintegration. 

 If E is the electromotive force, and L the resistance for a certain 



E . 



intensity when there is no luminous arc, T is the intensity , and 



E 2 L 



y- the entire quantity of heat developed by the current. If, on 



the contrary, aluminous arc is formed, and L expresses the entire 



resistance, — j — is the intensity, and ^—= — the quantity of heat 



produced. The work performed by the current in the luminous 



arc has its equivalent in the difference between these two quanti- 



E^-(E-D) 2 D(2E-D) T „ f , . . _., . 



ties, or 4= = ? -. It the resistance is 1/ and 



the intensity therefore different, the same equivalent becomes 



— r — y~i • If the mechanical work in the first case is A and 



in the latter A', we have thus A:A' = 1/:L. But the resist- 

 ances 1/ and L are inversely as the intensities. It follows thence, 

 finally, that the work performed by the current in the luminous arc 

 is proportional to the intensity so long as the electromotive force of 

 the battery remains constant. The work which the current per- 

 forms in the production of heat obeys the same law. The heat 



E 



produced is proportional to E . j- t ; and therefore, if E is constant 



proportional to the intensity, this equivalence between the two 

 cases, as is easily seen, would not occur if D were not indepen- 

 dent of the intensity. 



Second Series of Experiments. 



6. This series was undertaken in order to ascertain whether 

 and in what manner D could be dependent on the electromotive 

 force of the battery. Hence the experiments were made with a 

 different number of elements. Since new carbon points were 

 used in these experiments, which in hardness and other proper- 

 ties were different from those previously used, and since, more- 

 over, the solution of sulphate of copper used in the rheostat might 

 have altered in the interval between the two series, they cannot 

 be considered directly comparable. 



Experiment IV. The battery consisted of seventy-nine elements. 



