A certain merchant-ship touched on the coast of Syria, and the crew landed near the mouth of the river Belus, on a beach of fine white sand which, Pliny says, was still in his day of great repute for glass-making. The ship's cargo consisted of natron,--a natural alkaline crystal which was much used in ancient times for washing,[1]--and the crew having lighted a fire on the sand used lumps of it from the cargo to prop up their kettle. What was their surprise to find afterwards a stream of molten glass running down from their camp-fire. In this case the natron acted as a flux and enabled the sand to melt in the heat of the camp-fire, which, however, must have been a very large and hot one. [Sidenote: Egyptian glass.] Now, whether this story is true or not, it cannot have been the beginning of more than a local industry, for the art of glass-making was known in Egypt from very early times indeed. Its earliest use seems to have been in the imitation of precious stones, and perhaps for this reason it seems from the first to have been made in colours as well as in white; but the art of blowing it into vessels was certainly known in the fourth dynasty, and in some of the paintings in the tombs the process is actually represented. [Illustration: PLATE III METHUSELAH, CANTERBURY, ORIGINALLY IN CHOIR CLERESTORY Twelfth Century] It was not, however, till the first century of the Christian Era that any one seems to have thought of using glass to fill windows. In Egypt naturally the climate made it unnecessary, and even in Italy, where it can be cold enough in winter, civilization had evolved a style of architecture independent of glass. [Sidenote: Roman windows.] Nevertheless it was introduced in Rome under the first emperors. Caligula had his palace windows glazed, and Seneca mentions it as one of the luxuries which had been introduced into life in his time, but which did not really add to a philosopher's happiness. Its introduction was, however, very gradual, and even two centuries later its use was still quoted as evidence of excessive luxuriousness. Remains of these Roman windows have been found at Pompeii and elsewhere. At Pompeii they are in the form of small panes of glass held, in one case in a wooden, and in another in a bronze lattice.[2] It must be remembered that large panes were not available. Another method seems to have been to set panes of glass directly into small openings in stone-work. When coloured glass was first used in windows we have no evidence to enable us to say. As, however, the manufacture of coloured glass was already a flourishing art it cannot have been long before the idea came of using it to decorate windows. [Sidenote: St. Sophia.]