sphere, on which the succession of day and night depends--as well as to nurse mankind. In all this we see that the ruling principle and force of the kosmos ([Greek: to\ ê(gemoniko\n tou= ko/smou]) is made to dwell in and emanate from _its centre_. When we come to Aristotle, we find that the ruling principle or force of the kosmos is placed, not in its centre, but in its circumference. He recognises no solid revolving axis traversing the whole diameter of the kosmos The interior of the kosmos is occupied by the four elements--earth, water, air, fire--neither of which can revolve except by violence or under the pressure of extraneous force. To each of them rectilinear motion is _natural_; earth moves naturally towards the centre--fire moves naturally towards the circumference, away from the centre. But the peripheral substance of the kosmos is radically distinct from the four elements: rotatory motion in a circle is _natural_ to it, and is the only variety of motion natural to it. That it is moved at all, it owes to a _primum movens immobile_ impelling it: but the two are coeternal, and the motion has neither beginning nor end. That when moved, its motion is rotatory and not rectilinear, it owes to its own nature. It rotates perpetually, through its own nature and inherent virtue, not by constraining pressure communicated from a centre or from a soul. If constraint were required--if there were any contrary tendency to be overcome--the revolving periphery would become fatigued, and would require periods of repose; but, since in revolving it only obeys its own peculiar nature, it persists for ever without knowing fatigue. This peripheral or fifth essence, perpetually revolving, is the divine, venerable, and commanding portion of the kosmos, more grand and honourable than the interior parts or the centre. Aristotle lays this down (De Coelo, ii. 13, p. 293, b. 10) in express antithesis to the Pythagoreans, who (like Plato) considered the centre as the point of grandeur and command, placing fire in the centre for that reason. The earth has no positive cosmical function in Aristotle; it occupies the centre because all its parts have a natural movement towards the centre: and it is unmoved because there _must be_ something in the centre which is always stationary, as a contrary or antithesis to the fifth essence or peripheral substance of the kosmos, which is in perpetual rotation by its own immutable nature. I do not here go farther into the exposition of these ancient cosmical theories. I have adverted to Aristotle's doctrine only so far as was necessary to elucidate, by contrast, that which I believe to be the meaning of the Platonic Timæus about the rotation of the earth. LONDON: PRINTED BY W. CLOWES AND SONS, STAMFORD STREET, AND CHARING CROSS. **************************************************************** Transcriber's Note The text is based on versions made available by the Internet Archive.