Moses, in the original word אור _aur_, seems plainly to hint at the operation of a principle in the universe which, as a second cause, produced the phenomenon of _light_. This, most probably, was the motion of the luminous and fiery particles in the chaotic mass which, at the Divine command, separated themselves from the other gross materials of the miscellaneous composition, and by an attractive sympathy associated in one body. It is conjectured, that light was at first impressed on some part of the heavens, or collected in some lucid body. Dr. Wall says, Though the sun was not yet formed into a compact body, yet the most subtile and active particles had already begun to fly together to the centre of the solar system, which gave some light; though probably not so great as when afterward they made the compact body of the sun. And the earth, which was then only a round lump of mud, or muddy salt-water, being turned, as it has been ever since, upon its own axis, receiving that light on its several hemispheres successively, made night and day, or evening and morning. Milton gives his opinion in the following lines: “Let there be light! said GOD; and forthwith light Ethereal, first of things, quintessence pure, Sprung from the deep; and from her native east To journey through the aery gloom began, Spher’d in a radiant cloud; (for yet the sun Was not;) she in a cloudy tabernacle Sojourn’d the while.” Light, after a short progression, concentrated in the sun, the common centre of our system; the various parts of this system, by his central light or fire, are balanced, and, by mutual attraction, move in the expanse, according to fixed laws, or determined distances.[38] Light was once considered to be a property or quality of matter only; but more recently it has been discovered to be a _body_, a very subtile fluid, consisting of minute particles. We have no certain knowledge of its nature; though a collection of its rays make other things visible, yet its constituent parts themselves are most exquisitely small, and quite imperceptible; and therefore it approaches the nearest to the nature of spirit.[39] Of all material bodies, light is the most _simple_. Most others are compounded of several parts, not only of different, but sometimes of contrary natures: but light is an unmixed body. It is also a most pure matter; It has no defilement in itself, neither is it capable of contracting pollution from other objects. When it shines upon a dunghill or sepulchre, which sends forth the most offensive effluvia, it still remains uncontaminated. [The author is undoubtedly mistaken when he considers light “of all material bodies--the most simple,” and “an unmixed body.”