PHENOMENA MANIFESTED IN TELEGRAPHIC LINES, ETC. 307 



nomeiioii of au electrical discliarge. If we rightly understand it, the 

 theory given in this essay by Professor Donati is, that the sun and the 

 ])lanets, including the earth, are electrical, and that electrical discharges 

 may tal^e place from one to the other. This hypothesis has the supj)ort 

 of the fact that the earth is known to be a great charged conductor, per- 

 manently electrified negativelj^, and that the intensity of this electrical 

 condition is varied from time to time by perturbations produced by ter- 

 restrial, and, possibly, by cosmical causes. There is another theory ad- 

 vanced by the distinguished physicist Balfour Stewart, professor of 

 natural philosophy in Owen's College, Manchester, according to which 

 the sun and planets, like the earth, are great magnetic bodies, with op- 

 posite poles of greater intensity, subject to perturbations from cosmical 

 or special causes, and that these poles, acting by induction on the mag- 

 netism of the earth, give rise to the movements of the magnetic needle, 

 and to the induced electrical currents to which the appearance of the 

 aurora is attributed. 



There is still another hypothesis proposed by M. Becquerel as to the 

 origin of the electricity of the atmosphere and of the aurora polaris 

 which has been modified by M. Faye. This hypothesis, like that of 

 Herschel, refers the electricity of our atmosphere to the sun, and founds 

 the conception of it on the constitution of that luminary as revealed by 

 modern spectroscopic discoveries. From these discoveries the following 

 conclusions have been deduced : 



1st. The sun consists of a nucleus, relatively obscure, having a tem- 

 perature excessively elevated, and which is in a fluid state at least to a 

 certain depth. 



2d. This nucleus, on account of the cooling by radiation, is surrounded 

 by a terminated envelope which has the constitution of a gas with par- 

 ticles floating in or disseminated through it, of a solid or liquid nature. 

 These minute particles radiate energetically as do the particles of car- 

 bon in the flame of burning gas, and give to this envelope, which is 

 called the photosphere, its name and its luminosity. 



3d. Above the photosphere is found the chromosphere, formed princi- 

 pally of a thin layer of incandescent hydrogen. To this stratum appar- 

 ently belong the protuberances which of late years have excited so 

 much interest. 



4th. Lastly, above the photosphere is found a fourth atmosphere, 

 discovered during the last solar eclipse, which has been named the cor- 

 onal. This, which appears to be extremely rare, is very distinct from 

 the chromosphere, although formed of the same gas, namely, hydrogen. 



The foregoing propositions are considered as tacts immediate!}- de- 

 duced from the phenomena and well-established physical principles. 

 Tlie hypothesis as to the origin of this condition is that the nucleus of 

 the sun, as seen through the spots as a darker mass, is in reality much 

 hotter than the photosphere — so hot, indeed, as to prevent the union of 

 the oxygen with the hydrogen and the vapor of other substances 



