Dr. C. W. Siemens. 



[Mar. 2, 



Such a dense metallic atmosphere could not participate in the fan 

 action affecting the lighter photosphere, because this is only feasible 

 on the supposition that the density of the in-flowing current is, at 

 equal distances from the gravitating centre, equal or nearly equal to- 

 the outflowing current. It is true that the products of combustion 

 of hydrogen and carbonic oxide are denser than their constituents, 

 but this difference may be balanced by their superior temperature on 

 leaving the sun, whereas the metallic vapours would be unbalanced, 

 and would therefore obey the laws of gravitation, recalling them to 

 the sun. On the surface of contact between the two solar atmo- 

 spheres intermixture, induced by friction, must take place, however y 

 giving rise perhaps to those vortices and explosive effects which are 

 revealed to us by the telescope in the intermediate or stormy region of 

 the sun, and which have been commented on by Sir John Herschel 

 and other astronomers. Some of the denser vapours would probably 

 get intermixed and carried away mechanically by the lighter gases, 

 and give rise to that cosmic dust which is observed to fall upon our 

 earth in not inappreciable quantities. Excessive intermixture would 

 be prevented by the intermediary neutral atmosphere, the penumbra. 



As the whole solar system moves through space at a pace estimated 

 at 150,000,000 of miles annually (being about one-fourth of the velo- 

 city of the earth in its orbit), it appears possible that the condition of 

 the gaseous fuel supplying the sun may vary according to its state of 

 previous decomposition, in which other heavenly bodies may have 

 taken part. May it not be owing to such differences in the quality of 

 the fuel supplied that the observed variations of the solar heat may 

 depend ? and may it not be in consequence of such changes in the 

 thermal condition of the photosphere that sun-spots are formed ? 



The views here advocated could not be thought acceptable unless 

 they furnished at any rate a consistent explanation of the still some- 

 what mysterious phenomena of the zodiacal light and of comets. 

 Etesrardmsr the former, we should be able to return to Mairan's views, 

 the objection by La Place being met by a continuous outward flow 

 from the solar equator. Luminosity would be attributable to particles 

 of dust emitting light reflected from the sun, or by phosphorescence. 

 But there is another cause for luminosity of these particles, which 

 may deserve a passing consideration. Each particle would be electrified 

 by gaseous friction in its acceleration, and its electric tension would 

 be vastly increased in its forcible removal, in the same way as the fine 

 dust of the desert has been observed by Werner Siemens to be in a 

 state of. high electrification on the apex of the Cheops Pyramid. 

 Would not the zodiacal light also find explanation by slow electric 

 discharge backward from the dust towards the sun ? and would the 

 same cause not account for a great difference of potential between the 

 sun and earth, which latter may be supposed to be washed by the solar 



