Accordingly, the Pythagoreans constructed their system of the universe by the all-pervading and producing energy of this primordial agent, Number, in the manner thus described by Mr. Grote (i, 12-15): "The Pythagoreans conceived the Kosmos, or the universe, as one single system, generated out of numbers. Of this system the central point--the determining or limiting One--was first in order of time and in order of philosophical conception. By the determining influence of this central constituted One, portions of the surrounding Infinite were successively attracted and brought into system: numbers, geometrical figures, solid substances were generated. But, as the Kosmos thus constituted was composed of numbers, there could be no continuum; each numeral unit was distinct and separate from the rest by a portion of vacant space, which was imbibed, by a sort of inhalation, from the infinite space or spirit without. The central point was fire, called by the Pythagoreans the Hearth of the Universe (like the public hearth or perpetual fire maintained in the prytaneum of a Grecian city), or the watch-tower of Zeus. Around it revolved, from west to east, ten divine bodies, with unequal velocities, but in symmetrical movement or regular dance. Outermost was the circle of the fixed stars, called by the Pythagoreans Olympus, and composed of fire like the center. Within this came successively, with orbits more and more approximating to the center, the five planets, Saturn, Jupiter, Mars, Venus, Mercury; next, the sun, the moon, and the earth. Lastly, between the earth and the central fire, an hypothetical body, called the Antichthon, or counter-earth, was imagined for the purpose of making up a total represented by the sacred number ten, the symbol of perfection and totality. The Antichthon was analogous to a separated half of the earth, simultaneous with the earth in its revolutions, and corresponding with it on the opposite side of the central fire. The inhabited portion of the earth was supposed to be that which was turned away from the central fire and toward the sun, from which it received light. But the sun itself was not self-luminous: it was conceived as a glassy disk, receiving and concentrating light from the central fire, and reflecting it upon the earth, so long as the two were on the same side of the central fire. The earth revolved in an orbit obliquely intersecting that of the sun, and in twenty-four hours, round the central fire, always turning the same side toward that fire. The alternation of day and night was occasioned by the earth being, during a part of such revolution, on the same side of the central fire with the sun, and thus receiving light reflected from him; and during the remaining part of her revolution on the side opposite to him, so that she received no light at all from him. The earth, with the Antichthon, made this revolution in one day; the moon, in one month; the sun, with the planets Mercury and Venus,