210 Mr. J. Prideaux on the Theory of Voltaic Action. 



pencil to the perpendicular about 9°. The angle of the cone, 

 computed from these data, was found to be 1° 50'; differing 

 by 5' only from that assigned by theory. , r 9 rfj j 



Examining the emergent rays with a tourmaline plate, I 

 found that they were polarized, and according to the law 

 already observed in the former case of conical refraction. The 

 result was in this case predicted by theory ; in the former in- 

 stance it was first discovered by observation. 



XXXIV. On the Theory of Voltaic Action. By Mr. John 

 Prideaux*. 



Sect. I. Of the Relation between Voltaic and Common Electricity. 



1. "TJISTINCTIONS have been drawn between electricity 

 *-* from the machine, and that from the voltaic apparatus; 

 difference of tension having been considered insufficient to 

 account for the difference of their effects. Dr. Hare is, I be- 

 lieve, the only chemist who has offered an explanation of this 

 distinction, which he does by regarding voltaic as a compound 

 of common electricity and caloric. 



Because a) It warms all bodies through which it passes, 

 unless very good and sufficient conductors, of caloric as well 

 as of electricity. 



b) A wire may be made, by a strong voltaic current, to 

 continue radiating caloric for an indefinite time; which calo- 

 ric, unless indefinitely contained in the wire, must be supplied 

 by the current. 



c) By passing through charcoal, or other bad conductors of 

 heat, the caloric may actually be separated from the electri- 

 city, which is thus deprived of its heating power. 



And hence Dr. Hare names the operation of his apparatus 

 " calorimotion," in contradistinction to electromotion. 



2. Whether Dr. Hare has abandoned this theory, I do not 

 know. If not, it might be argued in reply, — 



a) That reducing the diameter of a good conductor, disen- 

 gages the heat as effectually, or even more so, than substituting 

 a bad one. 



b) That in reference to the wire, it may be made to give 

 out light indefinitely, by heat; supplied invisibly by hot airf, 

 or in any other mode, even that of the voltaic current ; whence, 



* Communicated by the author. 



t Over a flame of hydrogen gas, as near as possible without touching it, 

 hold a slip of platinum foil, edge downwards. The foil will continue to 

 glow so long as it and the flame are kept steady. The little platinum spiral 

 lamp, in vapour of spirit, is a more striking but less unequivocal evidence 

 of the same thing. 





