NEWTON S PBINCIPIA. 



137 



the body will always continue moving so as to shift its 

 place every instant and retain its position towards the 

 sun. In like manner, if any quantity of movable particles, 

 thrown off, for example, by the rotatory motion of the 

 earth, are in the hollow, they will not be attracted by the 

 earth, but only towards the sun, and will all accumulate 

 towards the side of the hollow sphere next the sun. So 

 of any fluid, whether water or melted matter in the hollow, 

 provided it do not wholly fill up the space, the whole of it 

 will be accumulated towards the sun. Suppose it only 

 enough to fill half the hollow space ; it will all be ac 

 cumulated on one side, and that side the one next the 

 sun; consequently the axis of rotation will be changed and 

 will not pass through the centre, or even near it, and will 

 constantly be altering its position. Hence we may be 

 assured that there is no such hollow in the globe filled 

 with melted matter, or any hollow at all, inasmuch as there 

 could no hollow exist without such accumulations, in con 

 sequence of particles of the internal spherical surface 

 being constantly thrown off by the rotatory motion of the 

 earth, 



If A H K B be a spherical section (or great circle), PRK 

 and PIL lines from the particle P, and infinitely near 

 each other, S D, S E perpendiculars from the centre, 

 and I q perpendicular to the diameter; then, by the 

 similar triangles P I R, P p D, we find that the curve 

 surface bounded by I H, and formed by the revolution 

 of IHKLI round the diameter AB, and which is 



