SPECTRUM ANALYSIS OF THE HEAVENLY BODIES. 149 
A remarkable nebula, and possibly one of the nearest to our system, of the 
nebule presenting a ring formation, is the well-known Annular Nebula in 
Lyra. The spectrum consists of one bright line only. When the slit of the 
instrument crosses the nebula, the line consists of two brighter portions cor- 
responding to the sections of the ring. A much fainter line joins them, 
which shows that the faint central portion of the nebula has a similar con- 
stitution. 
A nebula remarkable for its large extent and peculiar form is that known 
as the Dumb-bell Nebula. The spectrum of this nebula consists of one line 
only, A prismatic examination of the light from different parts of this 
object, showed that it is throughout of a similar constitution. 
The most widely known, perhaps, of all the nebule is the remarkable 
cloud-like object in the sword-handle of Orion. 
This object is also gaseous. Its spectrum consists of three bright lines. 
Lord Rosse informed the speaker that the bluish-green matter of the nebula 
has not been resolved by his telescope. In some parts, however, he sees a 
large number of very minute red stars, which, though apparently connected 
with the irresolvable matter of the nebula, are yet doubtless distinct from it. 
These stars would be too faint to furnish a visible spectrum. 
All the true Clusters, which are resolved by the telescope into distinct 
bright points, give a spectrum, which does not consist of separate bright 
lines, but is apparently continuous in its light. There are many nebule 
which furnish a similar spectrum. 
As an example of these nebule, the great nebula in Andromeda may be 
taken, which is visible to the naked eye, and is not seldom mistaken fora 
comet. The spectrum of this nebula, though apparently continuous, has 
some suggestive peculiarities. The whole of the red and part of the orange 
are wanting. Besides this character, the brighter parts of the spectrum have 
a very unequal and mottled appearance. 
It is remarkable that the easily resolved cluster in Hercules has a spec- 
trum precisely similar. The prismatic connexion of this cluster with the 
nebula in Andromeda is confirmed by telescopic observation. Lord Rosse 
has discovered in this cluster dark streaks or lines similar to those which are 
seen in the nebula in Andromeda. 
In connexion with these observations, it was of great interest to ascertain 
whether this broad classification afforded by the prism of the nebule and 
clusters, would correspond with the indications of resolvability furnished by 
the telescope. Would it be found that all the wnrcsolved nebule are gaseous, 
and that those which give a continuous spectrum are clusters of stars? 
Lord Oxmantown has examined all the observations of the 60 nebule and 
clusters in the speaker’s list, which have been made with the great reflecting 
telescope erected by his father, the Earl of Rosse. 
The results are given in the following Table :— 
Continuous spectrum. Gaseous spectrum. 
Guster anche states secei setae o« NOE ses en eecaatecaceen: 0 
Resolved, or resolved? ......... DU ecaue syaaace eeeerere rc 0 
Resolvable; or resolvable? ... 10 ........cececeseaceesoes 6 
Blue or green, no resolvability, [ O .......c.seccsseceseeses 4 
no resolvability seen ......... Gretiate eRe tteseaeceses 5 
31 15 
Not observed by Lord Rosse... 10.......c0...¢essssscees ay 
eM 19 
Considering the great difficulty of successful telescopic observation of these 
