200 Transactions.— Miscellaneous. 
In my paper on the Visible Universe,* I have given reasons to show that 
possibly the whole of the galactic poles consist of more or less diffused 
nebulous matter. As the reasoning, upon which I based this conclusion, 
appears to have been too condensed to be readily understood, I will give 
it a a little more in detail. Suppose the plane of the paper to contain 
the orbits of the two impacting bodies; when during the impact the centres 
of the two bodies are at their nearest point, it is probable the gaseous 
pressure produced by the impact will be near its maximum. It is certain 
that this pressure can only cause an escape of gas in a plane perpendicular 
to—and bisecting—the line joining the two centres of the two spheres. 
But the chief part of the material left by unbalanced momentum will be 
in the intersection of this plane and the plane of the paper, hence the only 
direction in which the pressure can act will be in a direction perpendicular 
to the plane of the paper. But this direction is the same as the axis of 
the resultant rotation due to the impact, and perpendicular to the plane in 
which the general mass of the matter will be distributed (which is clearly 
the plane of the paper). After the central mass has become free from the 
two bodies, the pressure will act in all directions, but the gas extended 
during the impact will more or less continue the direction it has taken, 
and will, doubtless, to a large extent separate itself from the other portions. 
As its direction will be perpendicular to the general movement, the polar 
nebular caps, and not unlikely all annular nebule which accompany the 
galaxy, were probably so formed. 
Having thus shown that the poles of the milky way were probably at 
one time covered with diffused nebulous matter, I will discuss the mode in 
which aggregations may be formed. It appears certain that any very large 
cosmical bodies would have myriads of bodies travelling around them in all 
orbits. In the case of the two large bodies which formed the Universe, it 
would, therefore, probably be so likewise. Many of these bodies would be 
entrapped by the outrushing gas, and would be carried with it in its journey. 
The gas would also meet the bodies already existing in the portion of space 
through which it travelled. At first, the temperature would be so high 
that the smaller bodies would certainly be heated and volatilized, but 
would render the mass more or less irregular, and these irregularities, if 
very considerable, would tend to increase themselves. The larger masses 
might form permanent nebule; in some cases, these would ultimately 
become stars. As the nebulous mass became colder, a peculiar selective 
action would not improbably tell upon it. If the temperature of the mass 
be uniform, the velocity of mean-square of the molecules of the several 
chemical elements will be inversely as the square-root of these molecules’ 
weight. A body travelling through this mass may have sufficient attractive 
* Vide ante, Art. XIII. 
