Intelligence and Miscellaneous Articles, 



167 



according to this physicist, each section of the current, having a real 

 intensity I and a duration a, must disengage during a vibration a 

 quantity of heat equal to KrVa. If the real intensity I is replaced 



T KrI, 2 



by its value 



the heat should be 



Other things being equal, 



a a 



it will be a minimum when a = 1 , that is, when the current is con- 

 tinuous ; it will increase when a diminishes, that is, when the du- 

 ration of each fragment of a current decreases. 



To verify this theoretical formula we used an ordinary Froment's 

 break. A platinum point fitted to a vibrating spring, on sinking, 

 dipped into a mercury-cup and transmitted the current ; it emerged 

 from it as it rose, and broke the current. The duration of each 

 fragment was prolonged by raising the level of the mercury, and was 

 diminished by lowering it ; the value of cc (that is, the duration of the 

 immersion) was easily measured. 



The following Table shows :— (1) that I lf the apparent intensity of 

 the broken current, may be calculated by Ohm and Pouillet's law, 



Aa 



and that it is equal to — , A being the electromotive force, and 



K-f r 

 R + r the total resistance of the circuit ; (2) that the quantity of heat 



rl 2 . 



developed in the resistance r, divided by — — , is a constant quantity 



a 



equal to K (K=0T9), whether the current is broken or whether it 



is continuous. 



Table I. — Values of K and of I } without Coil. 



(A=4l0-8, R = 3-65.) 



Intensity I r 





«= 



1. 



ct = 



0-06. 







Resist- 

 ance r. 











Ob- 



Calcu- 



C. 



K=^- 2 



c 



K=J^. 



served. 



lated. 





^ 





rl* 



14-40 



14-20 



25-30 



1080 



0-20 



1620 



0-18 



1545 



15 10 



23-62 



1160 



0-20 



1710 



018 



16-55 



16-63 



2104 



1150 



0-20 



1838 



019 



1890 



19-40 



18-12 



1120 



020 



2118 



019 



21-43 



21-23 



15-70 



1470 



0-20 



2120 



019 



24-16 



24-25 



13-25 



1640 



0-21 



2520 



0-19 



28-72 



28 82 



10-66 



1800 



0-20 



3820 



0-20 



35-60 



35-35 



7-97 



2150 



0-21 



3510 



0-20 



4470 



45-29 



5-42 



2490 



0-23 



4150 



0-20 

 019 









Means... 



0-20 





It is known that matters are not so simple when there is placed 

 in the circuit a coil containing soft iron ; the apparent intensity 

 of the discontinuous current is not given by the formula I x = la; it 

 is far smaller, and follows new laws now well known and investi- 

 gated by several physicists. Let us denote it by I' x ; it is obvious that 

 then each fragment of the current is very complicated — enfeebled at 

 the outset by the counter-current, and increased when it is broken by 

 the final shock (the extra current). It was probable that Joule's 

 law would be modified in a thermorheometer placed in the circuit. 



