BicxErton.—On Partial Impact, 125 
Art, VIIT,— Partial Impact: a possible Explanation of the Origin of the Solar 
System, Comets, and other Phenomena of the Universe. By Professor 
A. W. Bickerton, F.C.S., Associate Royal School of Mines, London. 
(Read before the Philosophical Institute of Canterbury, 1st August, 1878.) 
Iw the last paper which I submitted to the Institute, I gave a short sketch 
of some hypothetical cases of partial collisions, and suggested that such 
cases might possibly be of frequent occurrence throughout space, and might 
offer an explanation of many phenomena of the universe. I especially 
showed the application of the hypothesis to temporary and variable stars. 
To-night I intend to show that it appears competent to explain the 
formation of the solar system, of comets, of meteors, and of some variety of 
nebule. I shall, however, in the first place point out the very great dif- 
ference which exists in the capabilities of cases of partial and complete 
collision, the first offering a field of possibilities of cosmical phenomena 
which is really surprising, the latter being probably confined to but a few 
rare cases. 
In the last paper I assumed that the partial collision of two attracting 
bodies having an original proper motion in space, would be much more 
likely than entire coalescence. It appeared, however, to be a very general 
idea, that if the bodies struck at all, it must be that their mutual attraction 
would certainly produce complete coalescence. On the other hand, it was 
generally admitted that two bodies when attracted by each other would 
seldom come into contact, but would in most cases be carried by their 
original velocity away once more from each other’s influence. It is only 
necessary to assume that the size of the bodies has increased enormously 
without increase of mass for a case of mere disturbance to become one of 
partial collision ; the generality of the case is thus practically demonstrated. 
As cases of partial collisions may be of infinite variety, for the sake of 
simplicity I have in this paper (except where stated to the contrary) assumed 
that all the colliding bodies are of the same size; composed of the same 
chemical elements; with the same initial proper motions, the velocity of 
which is small compared with that developed by attraction; also that the ' 
mass of each of the two bodies of any one pair is the same. 
If two bodies come into direct collision from rest, a definite energy of 
velocity will be acquired at the moment of contact, depending solely on the 
mass. After coalescence, if a single particle were attracted from infinite 
space, the particle being attracted by the whole coalesced mass, and this 
mass not appreciably moving towards the particle, twice the force would act 
through twice the space, and would develope twice the velocity, or four 
times the energy. Hence, also, a particle to leave the body must have this 
double velocity. Therefore, as it does not appear reasonable to expect that 
