338 Mr. J. W. Mallet's Report on the Chemical Examination of Antiquities 



been the result of age ; unless indeed the bead had at some time been immersed 

 in oil or any similar fluid, which had penetrated it to the extent described. 



Two or three fragments oi jet examined proved, as might be expected, unal- 

 tered specimens of this varietj' of coal. 



COLOURED GLASS BEADS. 



These occur of several distinct colours ; the most common are, two shades of 

 blue, a black (in reality intensely deep green), a very pale sea green, and white ; 

 of each of which I received a specimen for qualitative analysis. 



No. 1 was a very fine dark-blue bead, from Kilmainham, quite resembling 

 good modern cobalt glass in colour, but full of minute air bubbles. By fluxing 

 with an alkali, solution in muriatic acid, and the application of the usual 

 re-agents, the colouring matter was found to be oxide of cobalt, but the glass 

 also contained a trace of copper. Whether the latter was accidental, or, being 

 known to tinge glass blue or green, was added with the intention of improving 

 the coloiu', it would be impossible to say. It was contended by Gmelin* that 

 the blue glass of the ancients was not stained by cobalt but iron (that it was 

 analogous to ultramarine) ; and an ancient specimen of a sapphire blue colour, 

 analyzed by KLAPROTH.f gave no indications of the former metal ; but Sir H. 

 DavtJ found cobalt in all the glass vessels of this colour from the tombs of 

 Magna Grsecia, and the same colouring material has been detected in the beads 

 found upon Egyptian mummies. The present is therefore but an additional 

 instance of the use of a compound of this metal for a special purpose being 

 known long before the metal itself or any of its preparations had been obtained 

 in a state approaching purity. 



No. 2. A bead of so dark a bottle-green colour as to appear by reflected 

 light quite black and opaque. In very thin splinters it was translucent, and 

 of the above tinge. The colouring material was oxide of iron, in very large 

 quantity, and traces of manganese were also distinctly perceptible. The spe- 

 cimen was from Templepatrick in the county of Antrim, nearly spherical, well 

 shaped, and liad a finely polished surface. 



No. 3 was a blebby, light blue bead, verging on green, from Kilmainham. 



• Gotting. gel. anz. 1776. f Beitrage. 6. 144. : Phil. Trans. 1815, p. 108. 



