Page:Archaeological Journal, Volume 7.djvu/487

Rh From this examination the Professor draws the following conclusions, which I give in his own words:—

1st. The external green colour of the glass is due to carbonate of copper.

2nd. The white coating which appeared under the green, chiefly consists of carbonate of lead, or white lead.

3rd. The interior part of the glass, so different in appearance from the exterior, nevertheless contains almost the same elements, but in a different state of combination.

4th. The red colour of the interior part of the glass undoubtedly is produced from protoxide of copper, which is present in considerable quantity, probably in combination with alumina.

5th. The green and white coatings of the glass are the result of a partial decomposition of the glass.

This examination becomes interesting from these facts, not only as showing us the knowledge possessed by the Romans in glass colouring, and therefore being important in an archaeological point of view, but inquiries of this nature are of great importance to the chemist. The art of making ruby glass was lost for a long period, and various have been experiments for recovering it; and though the method of producing this hue by copper has recently been fully explained by Cooper and Klaproth, it is not too much to say that had analyses of glass of this kind been made by early experimenters, much time and trouble would have been saved, and the comparatively inexpensive method of producing this colour by means of copper, when compared with gold, which has been used since the seventeenth century, would doubtless have superseded that very costly process.

I cannot conclude these remarks, therefore, without stating my conviction that the history of the past may derive much elucidation from modern science, and that the science and art of the present day may in their turn be greatly advanced by a correct examination and a due appreciation of what has been achieved in ancient times. I would also express the hope that antiquaries, whose attention is devoted to the examination of Romano-British remains, may be induced by the foregoing observations to devote a special attention to the nature of the materials employed in the works of decoration or construction, of which so many remarkable examples are almost daily brought to light. The aid of chemical science