RECENT PROGRESS IN PHYSICS 



403 



i Two series of experiments with an iron wire of 0.42 millimetre in 

 iiameter gave the iollowing results : 



FOURTH SERIES. 



Battery of 24 carbon-zinc cups. 



FIFTH SERIES, / 



Battery of 12 carbon-zinc cups. 



In siomc places. 

 Somewhat increased. 

 Intensely red hot. 

 Melted. 



f In reference to the experiments with iron wire it is to be remarked 

 'hat in each one a new piece was inserted, because by ignition the 

 urface was oxydized, and consequently the wire was altered. 



These experiments prove that one and the same loire produces, luith 

 he same strength of current, the same phenomena of ignition, whatever 

 nay be its length. 



In the platinum wire of 0.45 metre in diameter a partial ignition 

 s produced by a strength of current corresponding to a deflection of 

 t5° to 46°. With 40 elements this is effected in a wire of 1.3 

 netre in length, with 24 cups in one of 0.5 metre, and with 12 cups 

 n one of 0.4 metre. 



The red heat apjiears in all these experiments with a force of cur- 

 'ent of 48°, while in the first series the length of wire is 1 metre, in 

 ;he second 0.3 metre, and in the third 0.2 metre. 



The light red heat occurs with a strength of current of 50 to 51°. 



Quite similar are the results from the experiments with the iron wire. 

 Partial ignition ajjpears with a force of current of 82° to 33°, intense red 

 heat with 35°. These experiments therefore do not show the pecu- 

 liarity mentioned by Casselmann. It is to be regretted that he gives 

 no more exact details, from which perhaps the reason of the anomaly 

 observed by him could be explained. I presume, liowever, that it is 

 caused by the great conduction of heat by the mass of the metal in the 

 wire clamps, which has a considerable influence with very short wires. 



