344 
NATURE 
(Feb. 9, 1882 
some kind of reply ; but still, except in one respect, an 
indecisive one. It precludes at once the idea of a 
simple gaseous condition such as that of the Ring 
Nebula, or the Dumb-bell, or the wonder in Orion: 
d’Arrest eomplains indeed of the feebleness of the prin- 
cipal spectrum ; but all the three are continuous, as from 
stars. And yet they are peculiar, being deficient at the 
red end; at least this is expressly stated as to the central 
mass and the little ball. This peculiarity reappears else- 
where, not only among others in the beautiful nebulz 
M 81 and 82, in Ursa Major, which are as yet unresolved, 
but in the great Hercules cluster M 13, and surely indi- 
cates some difference from ordinary stellar light. And 
Fic 
unintelligible amount of pressure. If stellar, how 
are its components so concealed, that neither in 
its extreme brightness, surpassing much, as I have 
especially noted, the great Crion nebula, nor in the 
evanescent faintness of ifs wide diffusion can they be 
insulated? If stars are there they must be numbered by 
hundreds of thousands; yet possibly of much lesser 
magnitude than we, from ancient habit, are apt uncon- 
sciously to associate with the idea of a star. The exami- 
nation at least of many globular clusters has swept away 
old notions of size as well as distance; and there is no 
reason why bodies should not exist, not larger than the 
planets of our system, but emitting unborrowed light. 
And if such speculations may seem improbable, we may | 
again, as a fresh point of resemblance in general unlike- 
ness, M 13, as well as our two nebulae in Andromeda, is 
said by Huggins to have its continuous spectrum crossed 
either by lines of absorption or bright lines. So strange 
did this appear to that great observer that he was inclined 
to think in 1866 that perhaps the bright points in some 
clusters might not be of the same nature with true stars. 
At any rate the mystery, so far from being solved, seems 
only to be removed to a more inaccessible distance. 
What is that at which we gaze, overspreading field after 
field of the telescope with soft yet often vivid light ? 
If gaseous, gas unknown, or in some hitherto un- 
known condition, or as Newcomb remarks, under an 
il 
2.—Trouvelot, 1874. 
bear in mind that in verturing into these abysses we have 
intruded into a strange and mysterious region, where 
probabil'ty is left behind, and we have to deal with possi- 
bilities alene. 
What again are those rifts, which seemed so strange to 
Sir John Herschel that he sugge sted the idea of the inter- 
position of some less transparent material? Ofenings, 
perhaps, and indicating thinness of substance in the line 
of vision; openings which our earth, with its orbital 
velocity of 66,cco miles an hour, might possibly take 
years, possibly centuries, in crossing mcrely from side to 
side. This, however, must be observed, that they are not 
unparalleled in other nebulz.! But what, in any case, 
¥ Gen. Cat. 3r06 (Com, Ber.) ; 3132 (/'rgo); 3501 (Cape Obs) ; perbars 
