It is when we come to the blue, the dominant colour in this scheme of decoration, that a surprise awaits us. This colour, we should almost have taken for granted, would be derived from cobalt, for it is now recognised that at this time the use of that substance in the painting of earthenware (under the glaze) was prevalent in Western Asia. Dr. Linke, however, declares ‘that even the most subtle re-agents failed to discover any trace’ of either cobalt or copper in the blue enamel. For the grounds upon which he was able to attribute the origin of this fine blue to minute fragments of _lapis lazuli_, only partially dissolved in the flux, we must refer to the German chemist’s report. Now as ultramarine, the colouring matter of this mineral, contains a considerable amount of sulphur, some of it in an unoxidised state, it could not be used in combination with a flux containing lead, and indeed an analysis of the blue enamel proved it to be essentially of the same composition as the glass of the lamps; it contained, however, as much as 24 per cent of alkali, and this excess would ensure a slightly greater fusibility. It will be observed that the thick blue enamel on this Saracenic glass has considerable translucency as seen by transmitted light, but that the surface is always dull. In the British Museum is an admirably executed imitation of one of these mosque lamps, made as long ago as 1867 by M. Brocard of Paris. The blue, in this case cobalt, differs little in hue from that on the old lamps that stand beside it. It is, however, somewhat cruder in effect, and the surface is quite glassy.[110] [Illustration: _PLATE XXII_ FLASK OF ENAMELLED GLASS PROBABLY SYRIAN OR MESOPOTAMIAN. ABOUT 1300 A.D.] I come now to the scheme of decoration of this Saracenic glass. The important point to bear in mind is that the gold has for the most part disappeared from the surface. This gilding, however, played originally a most important part in the decoration. The fine lines of opaque red now so prominent were originally drawn with a free hand upon a detailed pattern of gold, with the object of accentuating the design. This gold brocading, when it is preserved, is of great beauty, especially that found upon the older pieces. Examine carefully the tall-necked bottle in the Slade collection: the body is covered with a fine arabesque of red lines, the pattern being made up of long-necked birds among foliage, and this appears poor in effect compared with the bands of rich enamel on the shoulder and neck. The effect, however, was very different at first when these dull red lines were carried over a rich ground of gold, of which traces only now remain here and there.