430 



KECENT PROGRESS IN' PHYSICS. 



shown in § 43. For the first of the above described series of experi- 

 ments the following temperature was obtained : 



for the other, 



T = 0.3975 ; 

 T — 0.0592. 



These numbers are to each other as 1 to 6.66 ; the fourth powers 

 of the corresponding diameters of the wires are as 1 to 6.738. The 

 temperatures, consequently, are very nearly as the fourth powers ot 

 the diameters, and are independent of the length of the pieces of wire. 



§ 39. Influence op breaks in the wire upon the rise of tempera- 

 ture. — A break in the closing wire has a marked influence upon the 

 temperature. When the ends of the broken wire were pointed, the 

 temperature was constantly lower than with an unbroken circuit, and 

 the lower, the farther the points of the wire were apart. This is ex- 

 plained by the fact that the residual charge of the battery becomes 

 greater as the distance the spark has to traverse is increased_, and 

 that consequently a less quantity of electricity passes through the 

 wire than when there is no interruption. 



Eemarkable phenomena appeared when Biess applied to the ends 

 of the wire two brass discs, 10.4 lines in diameter, which were kept 

 parallel to each other. The following table presents a part of the 

 results he obtained. 



For 0.1 line distance of the plates, the temperatures as a whole are 

 less than when they are in contact, yet the difference is much less than 

 might have been expected from the magnitude of the residual cliarge. 

 At a greater distance of the plates, for which a greater residue re- 

 mains, we are surprised to find temperatures sometimes even greater 

 than in the case of contact of the plates ; for weaker charges the tem- 

 perature is greater at 1 line distance than when the plates are in 

 contact ; on the contrary, with more powerful charges, the contact of 

 the discs produces a higher temperature. 



