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actions of vibration (with which it has nothing in the wide 
world to do), instead of the simultaneous “reaction” pre- 
dicated by Newton of pressure, &c. ; and the Gornhill writer 
sums up his article with a not illogical conclusion (partly 
quoted from some other author), which, if intended as science 
and not poetry, must have startled even some of the “ scien- 
tific, as well as more ordinary students in natural philosophy. 
He says : — 
“ If all natural action is vibration, involving opposite and equal actions, 
then the sum of it all equals — none. These opposites are like plus and 
minus , and they make up 0. i There never was a force in the universe for 
any one moment of action but there was another of equal force, acting in 
opposite direction. The sum total of all the forces in the universe is equal 
to — nothing ; — and has been so at every moment.’ ” 
With such ridiculous nonsense passing current amongst us 
as “ the very spirit of science,” need we be surprised that the 
“ Positive philosophers ” of our day, in like manner, profess 
to have found, that the great First Cause of all the Phenomena 
of this world is, also, only equal to 0 ? But to revert to the 
“ action and reaction ” referred to in the third law of motion, 
it is not unnatural to ask, — How, if every action were always 
opposed by an equal reaction , could the impression of force 
ever produce motion ? These opposites would really be “ like 
plus and minus ” ; and “ all the forces in the universe would 
indeed be = 0 ” ! Surely science and common sense must 
alike agree, that when bodies resist pressure, the degree of 
resistance (call it “ reaction ” if you please) depends upon the 
weight or quality of the body, and not upon the amount 
of pressure. When we press with the finger against marble, 
quicksilver, or water, with equally great force, we experience 
three different degrees of resistance from these three different 
material substances, arising from their different qualities of 
hardness or softness, solidity or fluidity, but having no de- 
pendence upon, nor equality with, the degree of force or 
pressure (or “ action ”) exerted upon them. 
37. But I must now pass on to notice, as I promised (§ 12), 
what appears in the 1st section of the Principia relating to a 
centripetal force : — 
“ Definition V . — A centripetal force is that by which bodies are drawn or 
impressed , or any way tend toivards a point as a centre. 
“ Of this sort is gravity, by which bodies tend to the surface of the earth ; 
magnetism, by which iron tends to the loadstone ; and that force, whatever 
it is, by which the planets are perpetually drawn aside from the rectilinear 
motions which otherwise they would pursue and made to revolve in curvi- 
