checks to send them back on their upward rebound. Again, if the void were finite, the infinity of bodies would not have anywhere to be. " Furthermore, the atoms, which have no void in them — out of which composite bodies arise and into which they are dissolved — vary indefinitely in their shapes ; for so many varieties of things as we see could never have arisen out of a recurrence of a definite number of the same shapes. The like atoms of each shape are absolutely infinite ; but the variety of shapes, though indefinitely large, is not absolutely infinite.' [For neither does the divisibility go on "ad infinitum" he says belom a ; but he adds, since the qualities change, unless one is prepared to keep enlarging their magnitudes also simply "ad infinitum."] ^ The atoms are in continual motion through all eternity. [Further, he says below, a that the atoms move with equal speed, since the void makes way for the lightest and heaviest alike.] Some of them rebound to a considerable distance from each other, while others merely oscillate in one place w*hen they chance to have got entangled or to be enclosed by a mass of other atoms shaped for entangling. 6 " This is because each atom is separated from the rest by void, which is incapable of offering any resistance to the rebound ; while it is the solidity of the atom which makes it rebound after a collision, expresses the same thing as " further on " or " below " in a modern book.