This was probably the crimson colour which the Frenchman, mentioned in the little account of Pompeii, published by the Society for the Diffusion of Knowledge, bought of the workmen employed in excavating the town, and used with success as a body colour. He does not appear to have analysed it, or in any way endeavoured to ascertain its nature, for the benefit of art. See vol. ii., p. 56. [247] See note to p. 8. [248] The colour of the mantle of the Ganymede in the ancient fresco belonging to Sir M. W. Ridley looks like discoloured lake. [249] Sir Humphrey Davy, in his paper in the first part of the volume of the Philosophical Transactions for 1815, on the colours used in painting by the ancients, says, that the artificial blue found in the baths of Titus is a frit made by means of soda, and coloured with oxide of copper. He imagines it to have been the blue invented by an ancient king of Egypt mentioned in the text, and the same also with that cœrulium, the art of making which was brought from Egypt to Puteoli, by Vestorius. That was made by heating together sand, flower of nitre, _i. e._ soda, and filings of copper. [250] Certain balls of a fine blue colour have been brought from the Egyptian tombs since Sir Humphrey Davy’s paper was written. I do not know whether they have been analysed, but their appearance is like that of the frit found in the baths of Titus. [251] She was of the Lusignan family, and is buried at Assisi. [252] It is to be regretted that Baron Bertholdy did not live to complete and publish his essay on the glass and paste of the ancients, as applied to the production of cameos, intaglios, &c., in imitation of true gems. He had collected a great mass of materials, and had had some very beautiful specimens engraved. Among other fragments, I saw in his possession, in 1819, several handles of drinking-cups, on which the maker’s name and place of residence, namely, Sidon, were stamped before the glass was cold, some in Greek, some in Roman letters. Mr. Hatchet has analysed many of the ancient glasses and pastes; but he did not find cobalt in any of them. In some very ancient beads found in one of the oldest tombs of Egypt, he found the colouring matter was manganese. Yet Davy speaks of a blue glass which appeared to him to be tinged with cobalt as common among the ruins of Rome; and says, moreover, that on analysing different ancient transparent blue glasses, he had found cobalt in all of them. [253] Pliny, book xxxiii. ch. 5. [254] Borax is a salt with excess of soda. The ancients used it as we do, as a flux, and a solder for metals. [255] Also used by shoemakers to blacken leather shoes. [256] Most probably Indian ink. [257] Purple dye, the purple of Puteoli, was not procured simply from the shell-fish, but was mixed with the juice of madder and the megalob berries. Hence, probably, the superior quality of the pigment.