and the Nature of Its Light. 4^ 



tonfiderable inequalities, there arife forms of all kinds which 

 exhibit no determined figure, until we become no more ac- 

 quainted with the fituation of the (hadows. On thcfummitsof 

 fiich eminences may be clearly feen rows of luminous points, 

 which, however, arife from a reflected light j but, on account 

 of their livelinefs, are taken for the luminous matter itfelf. 

 They feem to be, as it were, feparated portions of the folar 

 atmofphere, which float about within the conical cavities. 

 But on clofer examination this deception vaniflies. 



Laftly, fliould we fuppofe an atmofphere filled with clouds, 

 enlightened from above by the luminous matter, the great 

 blacknefs of the fpots, and the matter which furrounds them, 

 would oppofe fuch an idea. Such a continual phaenomenon 

 is founded on invariable caufes, and cannot be reconciled 

 with the changeable nature of clouds. A real folar land- 

 fcape may be recognized to be the fame before feen, even after 

 fome time, when the dire£lion of the light which falls upon 

 it has changed. 



It is more than conjefture that the fun feparates the lu- 

 minous matter from the firmament, and partly appropriates 

 it to itfelf and partly tranfmits it to other bodies, which, on 

 account of their lefs magnitude, are unable to ctfeft the fame. 

 As fo many ftars fliine with their own light, it is probable 

 that they all derive it from the fame fource; and that the 

 immenfe fpace of the firmament contains this all-enlivening 

 matter, which nature has dealt out with a fparing hand, and 

 feems to have de!tined for the moll important purpofes. 



The phaenonienon of the zodiacal light may be very natu- 

 rally explained according to thefe ideas. The feparation of 

 the light takes place more at the fun; it floats on its atmo- 

 fphere in exceedingly fmall quantity ; and, as it ftreams out 

 immediately in all direftions, the terreftrial bodies are fe- 

 cured from immoderate heat by this tendency to diverge. 

 The attraftion of the- luminous matter from the firmament 

 muft extend to a confiderable diiiance; for that fet free at 

 tlic fun is fupplied by another quantity, which feeks for an 

 equilibrium, and therefore forces itielf towards the folar equa- 

 tor. It accumulates therefore in thofe parts; and, as it is 

 half feparated, on account of the attraction of the fun adling 

 at that diftance, this mean ftate produces the palenefs of the 

 zodiacal light. This conjet^ure feems to be confirmed by a 

 remark of Caffini. At a time when the folar fpots were in- 

 vifible, no zodiacal light was to be feen. The abfence of the 

 fpots fliows a fuperabundance of the luminous matter on thu 

 fim ; confequently none is feparated, and thefe phaenomena 

 Hiuft ceafe. Were their feat in the folar atmofphere, they 

 4 • muft 



