186 Transactions.— Miscellaneous. 
In addition to the rotary motion in the plane of the paper, it will be 
seen that, from the distribution of the attractions and of the matter, 
pressure due to developed heat will act at first chiefly in a line passing 
through the centre of gravity and perpendicular to the plane of the paper, 
so that doubtless, in the majority of cases, a considerable proportion of 
gaseous matter will be found at the extremities of this axis. There appears 
considerable evidence that this is really the case with nearly all the ring 
nebule. But more careful investigation is needed on this point, as the 
drawings of different observers show considerable difference in this respect. 
It is certain that in the visible Universe nebulous matter lies chiefly at the 
poles of the galaxy. 
But the heat-motion acts in another way in addition to mere pressure. 
Heat is caused by the motion of molecules, and this motion tends to give 
an outward direction to the whole mass of the gas. This motion tells most 
in the lighter molecules, so that when any particle leaves its fellow, it 
proceeds directly outwards away from the mass. This action, in many 
cases, would doubtless convert the whole into a mere spheroidal shell, and 
it is extremely probable that this is the condition of the planetary nebule. 
But whenever the ratio, struck off at collision, is large, or there is a large 
ratio of heavy molecules present, these latter return again and form the 
star so often seen in the centre of these bodies. It would be worth while 
for members to consider a variety of the many cases which partial impact 
offers. A particularly interesting case is offered in which an impact is so 
considerable that the escaping parts are mere shells, doubtless this would 
break up, and strew the spiral with stars. And again, as regards the problem 
of the subsequent state of the ends of the spindle, a careful inspection will 
show that the forward velocity is very different on their two sides, doubtless 
tending to cause them sometimes to separate into a number of rotating 
masses, giving rise to multiple systems, having the peculiarity so charac- 
teristic of the motion of our Solar System. 
Thus it appears that rotation, matter chiefly in one plane, and high 
temperature proportional to mass, are the most striking general properties 
in partial impact, but that the many modifying causes may sometimes 
produce spirals or ring systems, in other cases mere gaseous shells, or in 
other cases densely-crowded systems, or complete dissipation of the whole 
matter into space. In fact, the field of possibilities appears nearly infinite. 
I think I have shown that it is almost certain that partial impact is at 
once the most frequent of definite cosmical phenomena, and at the same 
time a most powerful constructive agent in producing the many marvels 
which the monster tubes of the great astronomers have shown to exist in 
such endless variety in the heavens. 
