3 
relating to the Construction of the Heavens. 34,5 
or 2nd magnitude ; the brightest part is therefore 
probably not so far, - - - 322 
In thirty-seven years the nebulosity of this nebula has 
undergone great changes and much greater since 
the time of Hu yg hens, - 323 
Nebulae are not permanent celestial bodies, - 324, 
Additional proof of the opacity of the nebulous matter, 325 
Very distant nebulosities, which cannot be seen in a state 
of diffusion, may become visible when condensed into 
separate nebulae, -- 325 
Conversion of planetary into bright stellar nebulae, into 
stars with burs, or stars with haziness, - - 327 
Conversion of more distant ones into faint stellar nebulae ; 
into stars with burs, or with faint chevelure, « 329 
When it is doubtful whether an object is a star or a ne- 
bula, it may be verified by an increase of magnifying 
power, - 32 g 
When the object is very like a star, it becomes difficult to 
ascertain whether it is a star or a nebula, - 330 
When we cannot ascertain whether the doubtful object 
is a star or a nebula, of which several instances are 
given, the similitude is as great as any we can expect ; 
for were it greater, there could be no doubt, - 330 
I 
