384 



Miscellaneous Intelligence. 



and the one heated to a lesser degree positive. The same effects 

 are obtained if the two plates be of different metals. They are also 

 produced if the flame urg:ed by a blow-pipe be used. 

 ^ These phenomena may be supposed to result either from the fric- 

 tion of the flame on the metals, or from an electromotive action. 

 M.Becquerel inclines to the latter opinion, conceiving it improbable 

 that the tranquil flame of alcohol can produce friction sufficient to 

 suffice for the effect ; and not being able to account by friction for 

 the circumstance of two pieces of metal acquiring different elec- 

 tricities in the same flame, according to the temperature. That 

 the effect was not due to the difference of temperature existing in 

 various parts of the same piece of metal, was proved by the entire 

 absence of any electrical phenomena, when a plate of platinum was 

 heated to redness in the focus of M. Fresnel's strong burning 

 glass. These experiments have some relation to that of M. Volta 

 on the combustion of a piece of amadou at the extremity of a rod 

 communicating with the condensing plate of an electrometer. 

 W. Volta found, that when the apparatus was distant from habi- 

 tations, the amadou became positive by taking electricity from the 

 circumambient air, from which he concluded that the atmosphere 

 had always an excess of positive electricity. 



4. Electrical Phenomena accompanying ComiMS^io«.— M.Becquerel 

 found, that on rolling up a sheet of paper, placing it in the elec- 

 trometer, inflaming it, and touching the flame with a piece of wet 

 ■wood that the electricity might flow away more rapidly, the paper 

 became positively electrical. If the experiment were inverted, 

 the paper being held in the hand, and the flame made to touch the 

 piece of wet wood placed on the electrometer, it was found that 

 the flame took negative electricity. Hence it may be concluded, 

 ' that when paper is burnt, the paper becomes positive, and the flame 

 negative. 



If alcohol be burnt in a copper capsule, it is found by the con- 

 denser that the capsule becomes electrified positively. — Ann. de 

 Chim. xxvii. 14. 



5, On the Light of incavdcsccnt Bodies. — M.. Arago gave an 

 account of the experiments \\hich he had made long since on the 

 light which emanated from incandescent bodies. He ascertained 

 that this light, nlictherthc bodies were solid or liquid, was partially 

 polarised by refraction, when the ravs observed, formed an angle of 

 a small number of degrees with the surface from -whence they 

 came. As to the light of inflamed gases, it presented no sensible 

 traces of polarisation under any inclination. M. Arago draws as 

 a consequence from his experiments, that a considerable quantity 

 of the light by which we see incandescent bodies is formed in their 

 interior, at depths which have not as yet been completely deter- 



