THE PHYSICAL PHENOMENA OP OTHER WORLDS. 321 
lines well defined. The nebula (fig. 2) gave the three 
bright lines very sharp and distinct. This nebula/^ says 
Mr. Huggins, contains very probably a small quantity of 
matter condensed into a liquid or a sohd state."’^ The nebula 
(fig. 3) gave a spectrum which corresponded with that repre- 
sented; but, in addition to the three bright lines already 
named, a fourth bright line, excessively faint, was seen. 
Fig. 4 gave the brightest of the three lines well seen. The 
bright line looks remarkable, since it consists of two bright 
dots corresponding to sections of the ring ; and between these 
there was not darkness, but an excessively faint line joining 
them. The light from these nebula was so faint that no 
continuous spectrum could be detected. The celebrated 
Dumb-bell nebula,* in which points of light have been 
observed by Lord Rosse, Otto Struve, and others, was also 
carefully examined. The light of this nebula, after passing 
through the prisms, remained concentrated in a bright line 
corresponding to the brightest of the three lines represented 
in fig. 6, and this line was ascertained, by a simultaneous 
comparison with the spectrum of the induction spark, to 
agree in position with the brightest of the lines of nitrogen. 
None of the bright points alluded to gave continuous spectra. 
By suitable movements given to the telescope, those portions 
of the image were made to fall on the prisms. This method 
of observation showed that the light from different parts of 
the nebula is identical in refrangibility, and varies alone in 
degree of intensity. 
These remarkable researches launch us upon new fields of 
speculation, over which it is necessary to tread with extreme 
caution. Most of our astronomers have taught us to believe 
that the nebulae were clusters of stars, appearing nebulous 
only from their extreme distances from us. In support of this 
view, it has been shown that as the power of our instruments 
has been increased, many of these objects have been resolved 
into stars. ^‘"The reflector of Lord Rosse has resolved, or 
shown to be resolvable, multitudes of nebulae which had re- 
sisted the space-penetrating power of feebler optical instru- 
ments. Although there may be nebulae which this powerful 
telescope of six feet aperture shows only as nebulae, without 
any indication of resolvability ; yet from inferences founded on 
analogy, we may conjecture that in reality no difference exists 
between nebulae and clusters of stars.^^t brief, it may be 
stated that astronomers have generally adopted the hypothesis 
* See Observations on the Stars in the Dumb-beU Nebula, by M. 0. 
Struve, “ Phil, Trans.,” vol. 151, p. 738. 
t Sir John Herschel’s opening speech at the meeting of the British Asso- 
ciation at Cambridge, 1845. 
