.S7A 1 U'lIJ.IAM SIEMENS, I'.R.S. 307 



both their density and temperature had reached the necessary 

 elevation to induce combustion, each complete cycle taking, 

 however, years to be accomplished. The resulting aqueous 

 vapour, carbonic acid, and carbonic oxide would be drawn 

 towards the equatorial regions, and be then again projected into 

 space by centrifugal force. 



Space would, according to these views, be filled with gaseous 

 compounds in process of decomposition by solar radiant energy, 

 and the existence of these gases would furnish an explanation of 

 the solar absorption spectrum, in which the lines of some of the 

 substances may be entirely neutralised and lost to observation. 

 As regards the heavy metallic vapours revealed in the sun by the 

 spectroscope, it is assumed that these form a lower and denser 

 solar atmosphere, not participating in the fan-like action which is 

 supposed to affect the light outer atmosphere only, in which 

 hydrogen is the principal factor. 



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 inflowing cur- 

 rent is, at equal distances from the gravitating centre, equal or 

 nearly equal to the outflowing current. It is true that the pro- 

 ducts of combustion of hydrogen and hydrocarbons 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 con- 

 tact between the two solar atmospheres, intermixture induced by 

 friction must take place, however, giving rise to those vortices and 

 explosive effects within the zones of the sun, between the equator 

 and the polar surfaces, to which reference has already been made 

 in this article ; these may appropriately be called the " stormy 

 regions " of the sun, which were first observed and commented 

 upon by Sir John Herschel. Some of the denser vapours would 

 probably get intermixed, be carried away mechanically by the 

 lighter gases, and give rise to that cosmic dust observed to fall 

 upon our earth in not inappreciable quantities, and generally 

 assumed hitherto to be the debris of broken meteorolites. Ex- 

 cessive intermixture between the heat-producing atmosphere and 

 the metallic vapours below appears to be prevented by the 



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