is unlimited., and they all change into one another. The All includes the empty as well as the full. The worlds are formed when atoms fall into the void and are entangled with one another ; and from their motion as they increase in bulk arises the substance of the stars. The sun revolves in a larger circle round the moon. The earth rides steadily, being whirled about the centre ; its shape is like that of a drum. Leucippus was the first to set up atoms as first principles. Such is a general summary of his views ; on particular points they are as follow^. He declares the All to be unlimited, as already stated ; but of the All part is full and part empty . a and these he calls elements. Out of them arise the worlds unlimited in number and into them they are dissolved. This is how the worlds are formed. In a given section many atoms of all manner of shapes are carried from the unlimited into the vast empty space. These collect together and form a single vortex, in which they jostle against each other and, circling round in every possible way, separate off, by like atoms joining like. And, the atoms being so numerous that they can no longer revolve in equilibrium, the light ones pass into the empty space outside, as if they were being winnowed ; the remainder keep together and, becoming entangled, go on their circuit together, and form a primary spherical system. This parts off like a shell, enclosing within it atoms of all kinds ; and, as these are whirled round by virtue of the resistance of the centre, the enclosing shell becomes thinner, the adjacent atoms continually combining when they touch the vortex. a By the " full " is meant matter, atoms : by the " empty," space.