204 Transactions, — Miscellaneous. 
dition ; if not of great age, they are probably increasing their diameter, 
which may continue until they diffuse themselves into space. If very old, 
they have probably reached their limit of size, and the molecules may have 
so far lost their velocity by radiation during molecular impact, and by 
work done against the gravitating influence of the mass, as to be on their 
return journey, and in the act of forming themselves into a condensed 
nebula, and finally an ordinary star. It is singular. It is singular that it 
is only in the galactic zone that planetary nebulæ occur, and it is clearly 
in this zone that the great distribution of stars would lead us to expect many 
impacts. 
It appears possible to explain the origin of the annular nebule by partial 
impact in two different ways, and there may be representatives of both in 
the heavens, which will be found when the observation and classification of 
nebule are more satisfactorily done. In a former paper I have hinted at one 
of these methods, and the other explanation is the same as that given of 
the origin of the visible Universe, which would not improbably appear an 
annular nebula were it possible to see it ata sufficiently distant point in 
space (but which I have already shown, owing to the probable enormous 
distribution of small dark bodies in space, is unlikely,—as it is unlikely 
we see any distant universe). It appears that all annular nebule are more 
or less resolvable. There are many points of interest in connection with 
the origin of these small stars. Most of these have already been discussed 
in this paper in connection with the origin of nebule by aggregation ; but 
probably almost the entire ring consists of those parts of the original - 
bodies which were not very much affected by the impact as far as regards 
temperature, and much of this resolvable matter is not unlikely the dense, 
more infusible, part of the matter which very likely occupied the centre of 
the original bodies, and which was swept out into a circle, or rather two 
half-spirals, by the residual motion and attraction immediately after impact. 
There is one point in connection with the origin of the very slight eccen- 
tricities of all bodies moving in elliptical orbits (which is probably the con- 
dition of some of these bodies in annular nebule)—such as many double 
stars, and the members of our Solar System, whose nature has hardly been 
sufficiently noticed. On first passing away from the central mass, their 
motion is such that their orbit would be highly eccentric, if there were no 
agencies at work tending to render them circular. I have already shown 
that there are many such, and I will attempt to make this point clear. 
Supposing the body to leave in advance of the general body of the gas, to 
travel to its extreme distance, return and plunge into the body of the gas, 
when it has gone some distance into the gas the attraction acting upon it 
