The eminent critics, whose opinions I here controvert, have been apparently misled by the superior astronomical acquirements of the present age, and have too hastily made the intellectual exigencies of their own minds a standard for all other minds, in different ages as well as in different states of cultivation. The question before us is, not what doctrines are scientifically true or scientifically compatible with each other, but what doctrines were affirmed or implied by Plato. In interpreting him, we are required to keep our minds independent of subsequent astronomical theories. We must look, first and chiefly, to what is said by Plato himself; next, if that be obscure, to the construction and comments of his contemporaries so far as they are before us. In no case is this more essential than in the doctrine of the rotation of the earth, which in the modern mind has risen to its proper rank in scientific importance, and has become connected with collateral consequences and associations foreign to the ideas of the ancient Pythagoreans, or Plato, or Aristotle. Unless we disengage ourselves from these more recent associations, we cannot properly understand the doctrine as it stands in the Platonic Timæus. This doctrine, as I have endeavoured to explain it, leads to an instructive contrast between the cosmical theories of Plato (in the Timæus) and Aristotle. Plato conceives the kosmos as one animated and intelligent being or god, composed of body and soul. Its body is moved and governed by its soul, which is fixed or rooted in the centre, but stretches to the circumference on all sides, as well as all round the exterior. It has a perpetual movement of circular rotation in the same unchanged place, which is the sort of movement most worthy of a rational and intelligent being. The revolutions of the exterior or sidereal sphere (Circle of the Same) depend on and are determined by the revolutions of the solid cylinder or axis, which traverses the kosmos in its whole diameter. Besides these, there are various interior spheres or circles (Circles of the Different), which rotate by distinct and variable impulses in a direction opposite to the sidereal sphere. This latter is so much more powerful than they, that it carries them all round with it; yet they make good, to a certain extent, their own special opposite movement, which causes their positions to be ever changing, and the whole system to be complicated. But the grand capital, uniform, overpowering, movement of the kosmos, consists in the revolution of the solid axis, which determines that of the exterior sidereal sphere. The impulse or stimulus to this movement comes from the cosmical soul, which has its root in the centre. Just at this point is situated the earth, "the oldest and most venerable of intra-kosmic deities," packed round the centre of the axis, and having for its function to guard and regulate those revolutions of the axis, and through them those of the outer