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 

 retm-n 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 nebulae 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 nebulae by partial 

 impact in tAvo different ways, and there may be representatives of both in 

 the heavens, which will be found when the observation and classification of 

 nebulae 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 at a 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 nebula 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 nebulae 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 luilikely 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 nebulas) — such as many double 

 stars, and the members of oiu' Solar System, whose natiu-e 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 abeady 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 plmige into the body of the gas, 

 when it has gone some distance into the gas the attraction acting upon it 



