i88i.] 
The Evolution of the Spheres. 
129 
the adting force, whether impact, attradtion, or repulsion, 
In every case of impadt there is always an equal exchange 
of momentum. Where the motions of the impacting bodies 
are reversed, the new paths assumed exadtly replace the old 
paths lost. Where they move together after contadt the 
new path is the exadt equivalent of the two former paths. 
The heavier body necessarily suffers the least change in 
diredtion, otherwise the balance would be destroyed. 
It is the same with attradtion. Attradtions are always 
equal and opposite. Any body moved by attradtion causes 
by its opposite attradtion an equal reverse momentum in 
the adting substance. In repulsion it is the same ; both 
bodies are driven equally from the original path. 
If a small mass approach the earth its speed may become 
extreme, there being an apparent loss of motion in one 
diredtion or gain in the other. But the earth moves to- 
wards the falling body with equal momentum. Thus the 
gain of momentum in one diredtion by the body is precisely 
equalled by a reverse gain of momentum by the earth, and 
the great balance of force remains undisturbed. This prin- 
ciple, in fadt, cannot be overthrown by any conceivable 
adtion of force. The universe is a vast pendulum, where 
every forward swing of a particle is balanced by a simulta- 
neous backward swing of some other particle, moving with 
equal vigour. 
Necessarily, then, the positive motions now possessed by 
spheres must be balanced by equal opposite motions pos- 
sessed by other spheres, or else by an equal excess of motion 
in the opposite diredtion possessed by the matter of space. 
It is into this matter of space that the moving spheres have 
discharged their reverse motions. The particles of these 
spheres have thus lost a considerable portion of their ori- 
ginal motive energy, yet they retain a large percentage of 
it. They have lost a part of their motive energy in one 
diredtion, and move constantly forward in the opposite 
diredtion with a rapidity equal to the rapidity of the lost 
reverse motion. This may enable us to gain a more definite 
idea of the rapidity of the original motion. Every particle 
of the solar system moves through space at a speed of about 
250 miles per minute. Every particle of the earth moves 
around the sun at a speed of 1100 miles per minute. Every 
particle of the earth’s equator moves around the centre at a 
speed of 17 miles per minute. Yet these excessive speeds 
only indicate the speed of motion lost in the opposite direc- 
tions. In addition to this a considerable vigour of reverse 
motion is still retained, giving every particle rapid individual 
