232 Sir ISAAC NEWTO N’s Book III.

view to this great purpose. Upon the whole, the earth is evi-dently globular tho’ not an exact sphere, and if seen at a dis-tance would appear to us as the fun or moon ; that is, alwaysterminated by a circular figure, unless this distance was so greatas to make it appear like Venus or Mars ; when, in conse-quence os the contraction of the apparent diameter, the wholesurface would appear to be crouded in one point, and the Alps yPyrenees , and even the distant Cordelleras y would reflect un-distinguished rays. At such distances its figure could not bediscerned by sense, unless it was aflisted by a telescope or someequivalent instrument.

10. The ocean, which covers a great part of the surface osthe earth, is more accurately globular than the solid parts; andit is manifest that this arises from the gravitation of its parts to-wards the earth, acting in right lines perpendicular to its sur-face. For if its direction formed an acute angle with the sur-face, the fluid water would necessarily move towards that fide,and could not be in æquilibrio till the direction of gravity be-came perpendicular to the surface every where, so as to give noinclination to the fluid to move towards either side. The per-pendiculars to a spherical surface meet all in the centre os thesphere. Therefore, since the earth is nearly a sphere, the di-rection of the gravity is nearly towards its centre ; not as ifthere was really any virtue or charm in the point called thecentre, by which it attracted bodies, but because this is the re-sult of the gravitation of bodies towards all the parts of whichthe earth consists; as will appear more fully afterwards. Thedirection of gravity is not any one fixed or determined one, asthe vulgar are apt to imagine ; nor is there any occasion forpillars or instruments of any kind to support the earth ; that di-rection being always downwards which is towards the centre,or (to speak more accurately) which is perpendicular to the

1 fluid