Of this belief we find survivals among the early fathers, and especially in St. Ambrose. In his work on creation he tells us: "We must remember that the light of day is one thing and the light of the sun, moon, and stars another--the sun by his rays appearing to add lustre to the daylight. For before sunrise the day dawns, but is not in full refulgence, for the sun adds still further to its splendour." This idea became one of the "treasures of sacred knowledge committed to the Church," and was faithfully received by the Middle Ages. The medieval mysteries and miracle plays give curious evidences of this: In a performance of the creation, when God separates light from darkness, the stage direction is, "Now a painted cloth is to be exhibited, one half black and the other half white." It was also given more permanent form. In the mosaics of San Marco at Venice, in the frescoes of the Baptistery at Florence and of the Church of St. Francis at Assisi, and in the altar carving at Salerno, we find a striking realization of it--the Creator placing in the heavens two disks or living figures of equal size, each suitably coloured or inscribed to show that one represents light and the other darkness. This conception was without doubt that of the person or persons who compiled from the Chaldean and other earlier statements the accounts of the creation in the first of our sacred books.(8) (8) For scriptural indications of the independent existence of light and darkness, compare with the first verses of the chapter of Genesis such passages as Job xxxviii, 19,24; for the general prevalence of this early view, see Lukas, Kosmogonie, pp. 31, 33, 41, 74, and passim; for the view of St. Ambrose regarding the creation of light and of the sun, see his Hexameron, lib. 4, cap. iii; for an excellent general statement, see Huxley, Mr. Gladstone and Genesis, in the Nineteenth Century, 1886, reprinted in his Essays on Controverted Questions, London, 1892, note, pp. 126 et seq.; for the acceptance in the miracle plays of the scriptural idea of light and darkness as independent creations, see Wright, Essays on Archeological Subjects, vol. ii, p.178; for an account, with illustrations, of the mosaics, etc., representing this idea, see Tikkanen, Die Genesis-mosaiken von San Marco, Helsingfors, 1889, p. 14 and 16 of the text and Plates I and II. Very naively the Salerno carver, not wishing to colour the ivory which he wrought, has inscribed on one disk the word "LUX" and on the other "NOX." See also Didron, Iconographie, p. 482.