moved, or have their position; much less are those confused crowds of stars whirled around by the _Primum Mobile_, nor are they torn away and huddled along by a contrary and extremely rapid movement. Ptolemy of Alexandria seems to be too timid and weak-minded in dreading the dissolution of this nether world, were the Earth to be moved round in a circle. Why does he not fear the ruin of the Universe, dissolution, confusion, conflagration, and infinite disasters celestial and super-celestial, from a motion transcending all thoughts, dreams, fables, and poetic licences, insurmountable, ineffable, and inconceivable? Wherefore we are carried along by a diurnal rotation of the earth (a motion for sure more congruous), and as a boat moves above the waters, so do we turn about with the earth, and yet seem to ourselves to be stationary, and at rest. Great and incredible it seems to some philosophers, by reason of inveterate prejudice, that the Earth's vast body should be swirled wholly round in the space of 24 hours. But it would be more incredible that the Moon should travel through her orbit, or complete an entire course in a space of 24 hours; more so the Sun or Mars; still more Jupiter and Saturn; more than marvellous would be the velocity in the case of the {218} fixed stars and the firmament; what in the world they would have to wonder at in the case of their ninth sphere, let them imagine as they like. But to feign a _Primum Mobile_ and to attribute to the thing thus feigned a motion to be completed in the space of 24 hours, and not to allow this motion to the Earth in the same interval of time, is absurd. For a great circle of the Earth is to the ambit of the _Primum Mobile_ less than a furlong to the whole Earth. If the diurnal rotation of the Earth seem headlong, and not admissible in nature by reason of its rapidity, worse than insane will be the movement of the _Primum Mobile_ both for itself and the whole universe, agreeing as it does with no other motion in any proportion or likeness. It seems to Ptolemy and the Peripateticks that nature must be disordered, and the framework and structure of this globe of ours be dissolved, by reason of so swift a terrestrial revolution. The Earth's diameter is 1718 German miles; the greatest elongation of the new Moon is 65, the least is 55 semi-diameters of the Earth: the greatest altitude of the half moon is 68, the least 52: yet it is probable that its sphære is still larger and deeper. The sun in its greatest eccentricity has a distance of 1142 semi-diameters of the Earth; Mars, Jupiter, Saturn, being slower in motion, are so proportionately further remote from the Earth. The distances of the firmament and of the fixed stars seem to the best mathematicians inconceivable. Leaving out the ninth sphære, if the convexity of the _Primum Mobile_ be duly estimated in proportion to the rest of the sphæres, the vault of the _Primum Mobile_ must in one hour run through as much space