

WILLIAM SIEMENS, F.RS. 1 03 



only one-fourth reaches the earth itself. The amount of heat 

 radiated away from the sun would be represented by the annual 

 combustion of a thickness of coal 17 miles thick, covering its 

 entire surface, and it has been a source of wonderment with 

 natural philosophers how so prodigious an amount of heat could 

 be given off year after year without any appreciable diminution 

 of the sun's heat having become observable. 



Recent researches with the spectroscope, chiefly by Mr. Norman 

 Lockyer, have thrown much light upon this question. It is 

 now clearly made out that the sun consists near the surface, if 

 not throughout its mass, of gaseous elementary bodies, and in a 

 great measure of hydrogen gas, which cannot combine with the 

 oxygen present, owing to an. excessive elevation of temperature 

 (due to the original great compression), which has been estimated 

 at from 20,000 to 22,000 Fahr. This chemically inert and 

 comparatively dark mass of the sun is surrounded by the photo- 

 sphere, where its gaseous constituents rush into combustion, owing 

 to reduction of temperature in consequence of their expansion and 

 of radiation of heat into space. This photosphere is surrounded 

 in its turn by the chromosphere, consisting of the products of 

 combustion, which, after being cooled down through loss of heat 

 by radiation, sink back, owing to their acquired density, towards 

 the centre of the sun where they become again intensely heated 

 through compression and are "dissociated" or split up again into 

 their elements at the expense of internal solar heat. Great convul- 

 sions are thus continually produced upon the solar surface, resulting 

 frequently in explosive actions of extraordinary magnitude, when 

 masses of living fire are projected a thousand miles or more 

 upward, giving rise to the phenomena of sun spots and of the 

 corona which is visible during the total eclipses of the sun. The 

 sun may therefore be looked upon in the light of a gigantic 

 gas-furnace, in which the same materials of combustion are used 

 over and over again. 



It would be impossible for me at this late hour to enter 

 further upon speculations regarding the " regeneration of the sun's 

 heat upon its surface," which is a question replete with scientific 

 and also practical interest. We should always remember that 

 nature is our safest teacher, and that in trying to comprehend 

 the great works of our Creator we shall learn how to utilise to 



