which connect Light with Electricity. 257 



Besides, as the friction of the plate disengages variable quan- 

 tities of electricity, which also go on decreasing, it was neces- 

 sary to be independent of this cause of error. With this view 

 I made use of a good Leyden jar, the interior armature of 

 which communicated with the machine, and the exterior with 

 the lower wire of the tube. Here again the spark darted 

 from the great ball of the jar to that of the conductor inter- 

 rupted in the liquid of the tube, to a distance independent of 

 the colour of the glass which closed the opening of the case 

 (but less than that to which it passed by the mere discharge 

 of the jar itself). 



From the preceding researches, may we not conclude that 

 when light or electricity produces a chemical action, the lat- 

 ter is by no means modified by the presence of the other fluid, 

 whatever may be its quality and quantity? 



My results entirely agree with those of M. de Haldat*, 

 who found a complete nullity of influence of the electricity 

 which flows off thin wires on the phaenomena of diffraction 

 produced by the light passing the edge of these wires. They 

 also recall the observation of Mr. Faraday fj according to 

 which the state of tension produced by the passage of the 

 current from a strong pile through certain electrolytes, such 

 as some aqueous solutions of sulphate of soda and nitrate of 

 lead, or such as melted borate of lead, has no action on a ray 

 of polarized light traversing these liquids, either obliquely or 

 parallel to the direction of the current. 



2. Experiments to show that Electricity does not contain heat\. 



Does the electricity of tension contain heat, or are the 

 thermal effects which it causes only to be attributed to the 

 resistance of the conductors through which it passes ? This 

 problem, interesting in itself and in its applications, has been 

 resolved by Dr. P. Riess in his beautiful researches on the 

 heating properties of the discharge of the battery §. Yet this 

 solution is indirect and has not been the object of particulai 

 experiments; it is deduced from the two following laws: — 1st, 

 the quantity of heat set at liberty in a wire by a given electric 

 discharge is in direct proportion to the length and inverse to 

 the diameter of this wire ; 2nd, it depends on the nature of 

 the metal forming the wire. From this it follows, virtually, 

 that the discharge will not heat a wire of such dimensions, 



* Ann. de Chimie et de Physique, t. xli. p. 424. 

 f Experimental Researches, §§ 951 to 955. 

 \ From the Archives de V Electricite. 



§ P°gg- Ann., t. xl. p. 432; xliii. p. 47; xlv. p. 1. Repertorium der 

 Physik, t. vi. p. 191 (1842). 



Phil. Mas. S. 3. Vol. 23. No. 152. Oct. 1843. S 



