upon a smooth leaden tablet till the colours become trans- lucid and clear, and you again rub the piece of pottery upon the hone with saliva, and spread it upon a goat's skin smoothly fixed upon a wooden table; upon this you polish the electrum until it shine perfectly, so that if one-half be made wet, and the other remain dry, no one should be able to distinguish which is the wet part and which the dry."
Such is the mode of making these enamels, as described by Theophilus. With regard to the coloured glasses employed, we learn from the Twelfth chapter of the Second book, "De diversis coloribus vitri, non translucidis"—"Different kinds of glass found in Mosaic work, in the ancient edifices of the Pagans, namely, white, black, green, yellow (croceum), sapphire, red, and purple, and they are not clear but opaque like marble, and they resemble square stones, of which are made electra in gold, silver, and copper, of which we will speak fully in their place. Divers small vessels are also found of the same colours, which the French, very skillful in this work, collect, and the blue they melt in their furnaces, adding a little clear white glass, and they make plates of sapphire of great value, and very useful in windows. They make the like also of the purple and green." It appears then that it is to the ancient mosaics that the enameller of this period went for his store of coloured glass. Almost the only transparent colours to be found in remaining specimens are the blue, purple, and green, which supports the statement of Theophilus. The perfect preservation of the gold fillets, and the crystalline appearance of some of the transparent enamels, would lead one to suppose that the glasses were easily fusible, and that the objects were not exposed to a very high temperature; this is borne out by the presence of an opaque red enamel, in a specimen in the Museum of Practical Geology, which owes its colours to an oxide of iron, and at a high temperature would turn black."[1]
The metals which were used for the groundwork of these enamels appear, from the passage of Theophilus quoted above, to have been, gold, silver, and copper,—the only pure metals which were ever enamelled. Of these, gold, from its superior ductility and beauty, was doubtless most commonly
- ↑ I am indebted for this information to Sir Henry De la Beche, and take this opportunity of recording the kindness with which he has allowed me free access to the interesting series of enamels in the Museum of Practical Geology.
