116 The N.Z. Journal of Science and Technology. [April 
The ends of the axis at right angles to the plane of relative motion of 
the colliding stars are centres of regions of special weakness. The retreating 
stars are pulling in opposite directions, drawing the mass into a spindle 
shape with heavy material towards its ends. The sides of the spindle 
are temporary regions of weakness. The whole mass is rotating, and the 
stars themselves have new rotations impressed on those they had before. 
The volume of the third body is at first small compared with the stars, 
but its temperature is so great that the pressure produces the greatest 
explosion known in nature. . • 
The body grows with astonishing rapidity. For some days the outward 
rush of material is constantly accelerated by the pressure from within. 
The temperature being measured in millions of degrees centigrade, the 
pressure is correspondingly intense. Whilst the density is great, the 
confused molecular agitation gives light which, when analysed, shows a 
continuous spectrum. As soon as the molecules in the outer portions 
are free enough to execute their characteristic vibrations absorption-lines 
begin to appear. These lines necessarily show a progressive increase of 
their displacement towards the violet as long as the intense pressure of 
the exploding nucleus gives accelerated motion to the absorbing gases in 
the outer layers. 
The lines of many elements may be identified in this spectrum. 
When the collision occurs nearly all the kinetic energy of the portions 
which meet is transformed into molecular agitation. The third body is as 
hot as a body formed by the complete union of two suns meeting directly, 
for the same velocity of translation is destroyed in each case. But the 
resultant bodies have entirely different life-histories. In direct collisions 
of equal suns, with no original proper motion, the molecules of the com¬ 
bined body cannot have more, on an average, than half the energy corre¬ 
sponding to the critical parabolic velocity of escape ; the third body, formed 
by a grazing impact, has the same average molecular velocity, but this is 
many times as great as the critical velocity of escape from the mass of the 
third body. 
Just after the collision all the elements have the same molecular velo¬ 
cities and therefore widely different temperatures. Oxygen, for instance, 
is sixteen and lead 207 times as hot as hydrogen. The lighter elements 
must therefore gain, and the heavier elements lose, heat. During the out¬ 
ward rush atom-sorting begins. As hydrogen and helium gain velocity 
from the heavier elements they gradually find their way towards the outside, 
and ultimately form vast encircling spheres of gas. 
This brings about another change in the character of the spectrum. 
The third body grows to such vast dimensions that the radiation from the 
gaseous shells vies with and ultimately overpowers that of the nucleus 
itself. Further, since the gas is rushing out in every direction, it will give 
wide, bright bands. 
If the graze is a very slight one the velocity of the molecules will be 
many times the critical velocity, and the third body will be dissipated 
completely. The velocity of the outrushing gases after reaching its maxi¬ 
mum will hardly diminish at all, and therefore the bright bands will retain 
their full width until they fade away and disappear. 
The difficulties suggested in Adams’s paper vanish as soon as the 
peculiar characteristics of the third body are taken into account. 
This theory was published by Professor A. W. Bickerton in the 
Transactions of the New Zealand Institute in 1878, 1879, and 1880. 
