258 Professor Wartmann's Experiments to show 



whatever may be its nature, that it opposes no obstacle to the 

 flowing off of the fluid. 



The study of the cooling of electrified bodies (of which I shall 

 shortly make known the results) gave me an opportunity of 

 seeking a direct reply to the question proposed. For this 

 purpose I used a thermo-electric pile making part of Melloni's 

 apparatus, and consisting of bars of bismuth and antimony, 

 metals which have not engaged the attention of Dr. Riess. 



After having taken several precautions necessary for pre- 

 venting any foreign radiation from disturbing the results, by 

 the aid of a powerful electrical machine I caused a series of 

 sparks to pass from one face to the other. The needle of an 

 excellent rheometer by Gourjon, which closed the circuit, was 

 turned briskly, sometimes to the right sometimes to the left of 

 zero, whither it returned rapidly as soon as the production of 

 electricity ceased. Its movements then were not due to the 

 heat which the electricity might have produced*. They were 

 still visible when the circuit was open and when the rheome- 

 ter, insulated by a thick plate of glass, was connected only 

 with one pole of the pile. Lastly, the same effects were 

 produced when the spark was compelled to traverse the pile 

 from one pole to the other. 



It might be objected that the deviations of the needle were 

 produced by a derived or induced current, or by electrical 

 attractions and repulsions. To remove all doubt as to this, 

 I discharged a Leyden jar of moderate dimensions across the 

 pile from one pole to the other, and immediately closed the 

 circuit by plunging the conductors into the apertures of the 

 socket of the rheometer. Avoiding every heating agency 

 (such as the contact of the fingers, &c), at the points of 

 meeting of the copper wires with their terminal stems of brass, 

 I never perceived the slightest deviation. The experiment has 

 however been repeated many times both with the pile of Mel- 

 loni's apparatus and with a great thermo-electric pile of thirty- 

 six elements of bismuth and antimony intended for obtaining 

 the spark on mercury. 



Lastly, in order that the proof might be conclusive, it was 

 necessary to be certain that the result was not due to a per- 

 fect equality in the heating which the discharge had pi'oduced 

 at each similar and dissimilar soldering. For this purpose I 

 insulated upon a glass stand a thermo-electric element, having 



* It is well known that Prof. D. Colladon obtained as long ago as 1826 

 a deviation of the needle of the rheometer by the aid of the electricity of 

 tension, either of a machine or of a battery. See Ann. de Chim. et de Phi/s. 

 t. xxxiii. p. 62. 



