[ 473 ] 
of comets, and of our Earth, are more grofs in their 
nature, than the aetherial medium, which is generally 
diffufed throughout our folar fyflem. Poffibly a more 
aqueous vapour in the one than in the other, makes 
the difference. Now, as the atmofpheres of comets 
and planets, in our folar fyflem, are more grofs than 
the aether, which is generally diffufed throughout our 
folar fyflem, why may not the aetherial medium dif- 
fufed throughout thofe other folar fyflems, (whofe 
centers are their refpedlive fixed flars) be more grofs 
than the aetherial medium diffufed throughout our 
folar fyflem ? This is, indeed, an hypothecs, but 
fuch an one as agrees exa&ly with nature. For thofe 
nebulous flars appear fo much like comets, both ta 
the naked eye and through telefcopes, that the one 
cannot always, by any difference of their extraneous 
light, be known from the other. 
Such orbs of grofs asther, reflecting light more co- 
pioufly, or like the atmofpheres of comets, may help 
us to judge of the magnitudes of the orbs illuminated 
by thofe remote funs, when all other means feem to 
fail. 
The appearance of new flars, and difappearance of 
others, poflibly, may be occafioned by the interp®fi- 
tion of fuch an aetherial medium, within their re- 
fpcdtive orbs, as either admits light to pafs freely, or 
wholly abforbs it at certain times, whilff light is con- 
flantly purfuing its journey, through the vafl regions 
of fpace. 
LXXIII. Ex- 
V p p 2 
