and its Effects, 125 



tion at the ends of the induction wire : both are produced by 

 the resistance which the air opposes to tlie passage of electricity. 



The first-mentioned accumulation is now prevented by Fi- 

 zeau^s happy idea of employing a condenser, for by it the accu- 

 mulated electricities can flow quickly out of the inducing Avire, 

 without a closed circuit being formed. 



The quantity of electricity in the induction wire is not in- 

 creased by the condenser. This is easily shown by closing the 

 induction circuit after introducing a magnetometer into the same. 

 The deviations which are obtained in the latter instrument at 

 each time of opening and closing the inducing current are not 

 only equal to one another, but are as great without the condenser 

 as with it*. 



The generation of electricity in the induction wire at the 

 moment of breaking the inducing current is, however, accelerated 

 by means of the condenser, and consequently the tension of the 



* From tlie followiug considerations it is well known that the equality 

 of the quantities of electricity which are generated may be concluded from 

 the equality here mentioned. If, at one time, through a section of the 

 wire, a quantity of electricity equal to unity passes in the unit of time, so 

 that an intensity of current and a deviation, each equal to unity, are ob- 

 tained , and if, at another time, the unit of electricity passes through the 

 same section in ten imits of time, the intensity of current will be equal to 

 one-tenth, and cousec[uently the deviation in the unit of time will be one- 

 tenth; therefore in the whole time it will be =10-i-^, that is, it will be 

 again =1; provided, of course (which has been assumed throughout), 

 that the whole time of passage is so small in com)jarisoii to the time of 

 oscillation of a magnetic needle that the single impulses will strike the 

 needle in about the same situation, that is to say, not far distant from its 

 position of rest. 



It is otherwise with the quantities of heat which are developed at the 

 opening and closing of the circuit ; inasmuch as these are proportional to 

 the squares of the intensities of the cun-ent, and not (like the deviations) 

 directly proportional to the same, we cannot conclude the equality of the 

 quantitiesof heat from the equality of the quantities of electricity which are 

 generated, unless the times in which they are generated are also equal, 

 for example, if at one time through a certain section the unit of electricity 

 passes in the unit of time, so that an intensity of ciuTent and a quantity of 

 heat, each equal to unity, are obtained^ and if at another time through the 

 same section the unit of electricity passes in the time ten, then the inten- 

 sity of current will be equal to one-tenth, consequently the quantity of 

 heat generated in the unit of time will be =tcto> f^n*^ 'u the whole time of 

 passage will be =10'^i^=-j'^, therefore it will be ten times smaller; that 

 is, inversely proportional to the time of passage. 



Hence, if the equality of the quantities of electricity which are generated 

 be proved by means of the magnetometer, the relation between the times 

 of generation may be determined by means of the electric tliermometer. 

 Instead of the latter instrument, the electric dynamometer, which W. 

 Weber has already employed for such detei-minations (Pogg. Ann. vol.lxxiii. 

 p. 21 5 j, could be used. Even a galvanometer with a soft iron needle would 

 determine, ajiproximately, the duration of the times of generation. 



