But what is the meaning of evening and morning, if these days were long periods? Here fewer difficulties meet us. First: It is readily conceivable that the beginning and end of a period named a day should be called evening and morning. But what made the use of these divisions necessary or appropriate? I answer that nature and revelation both give grounds at least to suspect that the evening, or earlier part of each period, was a time of comparative inaction, sometimes even of retrogression, and that the latter part of each period was that of its greatest activity and perfection. Thus, on the views stated in a former chapter, in the first day there was a time when luminous matter, either gradually concentrating itself toward the sun, or surrounding the earth itself, shed a dim but slowly increasing light; then there were day and night, the light increasing in intensity as, toward the end of the period, the luminous matter became more and more concentrated around the sun. So in our own seventh day, the earlier part was a time of deplorable retrogression, and though the Sun of Righteousness has arisen, we have seen as yet only a dim and cloudy morning. On the theory of days of vision, as expounded by Hugh Miller, in the "Testimony of the Rocks," in one of his noblest passages, the evening and night fall on each picture presented to the seer like the curtain of a stage. Secondly: Though the explanation stated above is the most probable, the hypothesis of long periods admits of another, namely, that the writer means to inform us that evening and morning, once established by the separation of light from darkness, continued without cessation throughout the remainder of the period--rolling from this time uninterruptedly around our planet, like the seal cylinder over the clay.[54] This explanation is, however, less applicable to the following days than to the first. Nor does this accord with the curious fact that the seventh day, which, on the hypothesis of long periods, is still in progress, is not said to have had an evening or morning. (3.) It is objected that the first chapter of Genesis "is not a poem nor a piece of oratorical diction," but a simple prosaic narrative, and consequently that its terms must be taken in a literal sense. In answer to this, I urge that the most truly literal sense of the word, namely, the _natural_ day, is excluded by the terms of the narrative; and that the word may be received as a literal day of the Creator, in the sense of one of his working periods, without involving the use of poetical diction, and in harmony with the wording of plain prosaic passages in other parts of the Bible. Examples of this have already been given. It is, however, true that, though the first chapter of Genesis is not strictly poetical, it is thrown into a metrical form which admits of some approach to a figurative expression in the case of a term of this kind.