) 
Sir R. Phillips's Defence of his Hypothesis. 209 
they agree with his hypothesis: hence, it is difficult to refute 
such undefined opinions. Undoubtedly Sir R. thinks that he 
has corrected the mistake, and therefore rendered the demon- 
stration in the Phil. Mag. for July, p. 436, correct ; in this, 
however, he is mistaken. The demonstration is mtended to 
prove that bodies are deflected towards the earth by a power 
which decreases inversely as the square of the distance. Now 
it is evident, that a projectile or mass of matter can be acted 
upon by that part of the spheric surface only which it occupies 5 
also, that it cannot occupy similar portions of spheric surfaces ; 
—but it is similar portions only that are to one another as the 
squares of their radii: therefore, the conclusion is equally as in- 
correct as it was before. And, as a proof that circular motion 
has not any effect to impel a body towards the centre of motion ; 
place an open vessel of water upon the internal part of the rim 
of a wheel, and turn the wheel with considerable velocity; when 
the water will acquire such.a degree of centrifugal force as will 
retain it in the vessel, in all positions of the wheel. Again, if a 
ball or other body were made fast upon the external part of the 
rim of the wheel, and it were put in motionwith a considerable 
velocity; then could the power that confines the ball to the 
wheel be suddenly removed, the ball would fly off in a tangent 
to the rim of the wheel. ’ 
As either of these experiments might be tried*without much 
difficulty, I would recommend them to Sir R’s notice; though it 
be now too late to save him from exposing his ignorance of the 
laws of motion, (see his answers to the second and third objee- 
tions,) it may prevent a repetition of a like exposure. 
Sir Richard has certainly adopted a very singular mode of 
defending himself; for he assumes the most questionable part 
of his hypothesis, to be an established truth, (viz. the deflective 
power of the rotary motion,) and then proceeds to reply to the 
minor objections, by telling us, over and over again, that the 
deflective power of the rotary motion is equivalent to gravita- 
tion.—OF course, if that were the case, it would produce the 
same effects. But Sir R. has not anywhere shown that it ts 
equivalent—nay, not even that it has the least tendency to de- 
flect a projectile towards the earth. | 
If Sir R. would take the trouble to define the sense in which, 
he uses the word motion, it would then be a little more clear 
how far it is better known than gravitation. According to the 
common definition of the term, motion is only an effect; of 
which it is the object of the philosopher to inquire the cause. 
Newton and others have shown gravitation to be one of the 
camses of the rotary and orbicular motions of the planets, of the 
flux and reflux of the ocean, the descent of projectiles, and, 
Vol. 50. No. 233, Sept. 1817. O various 
