I have said that the Hebrew word translated "light" includes the vibratory movements which we call heat and electricity as well. I make this statement, not intending to assert that the Hebrews experimented on these forces in the manner of modern science, and would therefore be prepared to understand their laws or correlations as fully as we can. I give the word this general sense simply because throughout the Bible it is used to denote the solar light and heat, and also the electric light of the thunder-cloud: "the light of His cloud," "the bright light which is in the clouds." The absence of "_aur_," therefore, in the primeval earth, is the absence of solar radiation, of the lightning's flash, and of volcanic fires. We shall in the succeeding verses find additional reasons for excluding all these phenomena from the darkness of the primeval night. The light of the first day can not reasonably be supposed to have been in any other than a visible and active state. Whether light be, as supposed by the older physicists, luminous matter radiated with immense velocity, or, as now appears more probable, merely the undulations of a universally diffused ether, its motion had already commenced. The idea of the matter of light as distinct from its power of affecting the senses does not appear in the Scriptures any farther than that the Hebrew name is probably radically identical with the word ether now used to express the undulating medium by which light is propagated; and if it did, the general creation of matter being stated in verse 1, and the notice of the separation of light and darkness being distinctly given in the present verse, there is no place left for such a view here. For this reason, that explanation of these words which supposes that on the first day the _matter_ of light, or the ether whose motions produce light, was created, and that on the fourth day, when luminaries were appointed, it became visible by beginning to undulate, must be abandoned; and the connection between these two statements must be sought in some other group of facts than that connected with the existence of the matter of light as distinct from its undulations. What, then, was the nature of the light which on the first day shone without the presence of any local luminary? It must have proceeded from luminous matter diffused through the whole space of the solar system, or surrounding our globe as with a mantle. It was "clothed with light as with a garment," "Sphered in a radiant cloud, for yet the sun was not."