130 Constancy of Solar Light and Heat. 



changed. At such a temperature many, perhaps all, chemical 

 compounds are dissociated into their elementary parts. Were all 

 the elements of the sun dissociated by reason of an uniform pre- 

 vailing temperature, their gradual recombustion, and exertion 

 of their chemical affinities, would maintain the constant tempera- 

 ture of the sun for a prolonged period of 8000 years. Neither 

 Original heat alone, nor Original heat combined with chemi- 

 cal attraction, are, therefore, sufficient to continue the solar 

 activity for an indefinite time. These two operations may be 

 seen in action together in a fireball with a permanent streak of 

 light. The fragments of the meteor are red in light, and rapidly 

 disappear as their temperature falls and vanishes by radiation. 

 The streak is of immensely higher temperature, and the recom- 

 bustion of its dissociated vapours maintains the high tempe- 

 rature at a constant value for many seconds, and occasionally 

 for many minutes after the disappearance of the fragments. A 

 continual repetition of meteors would be required to supply the 

 earth with incessant light from such a source, and such a suc- 

 cession of meteors is therefore supposed to occur upon the sur- 

 face of the sun. It is calculated that a yearly deposit sixty-six 

 feet in depth of solar satellites would actually suffice to maintain 

 the present supply of solar light and heat unchanged : a 

 quantity much too minute to be perceived in less than many 

 thousand years by angular measurements of the sun's diameter. 

 The light and heat of meteors upon the earth are confined 

 to the highest strata of the atmosphere. It appears that this 

 is equally the case upon the sun, and that the meteoric particles 

 from their minuteness are consumed, and all their elements 

 (1 i ssociated at the boundary of the solar atmosphere. Their fiery 

 streaks alone remain. Like steam condensing into water, these 

 maintain their high temperature until all the elements have 

 re-combined and dispersed abroad their latent heat. Such 

 streaks are actually seen upon the sun as straw-like or leaf-like 

 lines, which intersect each other in every conceivable direction. 

 W'licn cooled, the matter must descend as dust or in drop-like 

 pieces upon the surface of the sun. The spots which appear 

 upon the luminous envelope of the sun may arise whenever an 

 aerolitic mass of large dimensions penetrates to the solar surface 

 unconsumed, and with volcanic violence destroys the order of 

 the atmospheric si rata where it strikes. The spots are far 

 removed from the solar poles, and therefore near the piano of 

 tlio ecliptic where the planets have their orbits; but the loaf- 

 like Lines are seen over every portion of the sphere of the 

 sun, like fireballs at the surfaco of the earth. Chemical affinity 

 may thus be said to act the pari of a damper and regulator of 

 the solar fires, reserving portions of tho heat suddenly imparted 

 to the sun, and again maintaining its uniformity of tempera- 





