236 Intelligence and Miscellaneous Articles. 



Our machine consisted of six rotating plates, each provided with 

 sixteen bobbins joined in tension and forming a total resistance R of 

 twelve turns of the rheostat. These plates are joined in quantity, so 

 as to form an electromotor of six independent machines sending their 

 electricity into a common external circuit. The resistance of the whole 

 is then equal to R divided by 6, or to two turns of the rheostat. In 

 each series of experiments the velocity remained constant; it varied 

 in the different series from 350 to 550 turns in a minute. The ma- 

 chines were driven by a Hugon's gas motor, the regularity of which 

 has been proved to be perfect. By means of a brake on the principal 

 shaft, the force, and therewith the heat imparted to the machine, 

 could be regulated and measured. The heats regenerated in the ex- 

 ternal resistances were measured under the usual conditions. 



All the experiments showed that the number C of thermal units 

 thus regenerated in an external resistance increases as this resistance 

 increases, diminishing then to zero when it becomes infinite. It 

 attains a maximum for a value of x equal to R, or to twelve turns of 

 the rheostat ; it is exactly represented by the formula 

 p _ xAr 

 ~"(R + 2 ' 



But we know that in an external circuit x of a battery whose elec- 

 tromotive force is A and the internal resistance R, the heat regene- 

 rated is expressed by Joule's formula, 



C = xi\ 

 or by 



(R+*) 2 



The magneto-electrical machine behaves, then, as this battery 

 would — with, however, an essential difference, which is that R 



does not represent its real internal resistance, which is — , but that 



6 



of each of the plates or of each of the electromotors which concur in 

 producing the total current. We may say, then, that Ohm's law 

 applies to the magneto-electrical machine with an essential modifi- 

 cation, by supposing that each of the various plates is independent, 

 and that its currents accumulate on the external circuit. 



There is an important difference between the battery and the ma- 

 chine. The quantity of heat C x furnished by the battery in a given 

 time is proportional to the electromotive force and the weight of zinc 

 dissolved— that is, to the intensity of the current ; so that we have 



0- A 



~K+x' 



which shows that this heat varies as the ordinates of an equilateral 

 hyperbola. But the magneto-electrical machine seems to be only a 

 battery which borrows its heat from a motor instead of taking it from 

 a chemical action, and we might be led to suppose that the quantity 

 of heat furnished should vary according to the same law. This is 

 not the case. The quantity is represented by the empirical relation 



