And thus "the witchery of the soft blue sky" launches us naturally into the subject of the sky as colour; and not of blue only, but of that vast range of hues and gradations which display their beauty and their glory in the four quarters of heaven during each move onwards of the earth from sunrise to sunrise. Tennyson's description is vivid and splendid. The shipwrecked Enoch Arden is waiting for a sail, and sees "Every day The sunrise broken into scarlet shafts Among the palms and ferns and precipices; The blaze upon the waters to the east; The blaze upon his island overhead; The blaze upon the waters to the west; Then the great stars that globed themselves in Heaven, The hollower-bellowing ocean, and again The scarlet shafts of sunrise." But of special interest here is the fact that the blue of the vault is never mentioned--only the scarlet shafts of sunrise and the blaze. Whether this omission was intentional or not, may be uncertain. But it brings to mind the strange fact that the perception and naming of this blue are comparatively recent acquirements. In the old hymns of the Rigveda the chariot of the sun is described as glowing with varied colour, and its horses as gold-like or beaming with sevenfold hues; but although there was a word for the blue of the sea and for indigo dye, this word is never applied to the brightness of the sunlit vault. So, still more strangely, we find that notwithstanding the laughing blue of the Greek sky, old Homer never calls it blue! He has his rosy-fingered dawn, the parallel of Tennyson's scarlet shafts; but the daylight sky seems to have been for him as for Enoch Arden, a "blaze." Nor is the omission supplied in the later classical literature; and the older Greek writers on science use such epithets as "air-coloured," as substitutes for more specific terms. A German scholar who has examined the ancient writings of the Chinese claims for them priority in the recognition of the blue of the sky, and points out that in the Schi-king, a collection of songs from about 1709 to 618 B.C., the sky is called the vaulted blue, as in the more modern language it is called the reigning blue. Delitzsch, from whom much of what is just stated has been derived (as also from Gladstone's paper on Homer's colour-sense) does not find the blue of the sky recognised in Europe earlier than the oldest Latin poets of the third century B.C., who use _caerulus_ of the sky, and henceforth this epithet takes its place in literature, Pagan and Christian. And the appreciation of the heaven-colour develops apace until we have Wordsworth's "Witchery of the soft blue sky."