copper, and the blue with iron. The latter dark azure iron-blue was, probably, the produce of the Alexandrian furnaces, at a very early period of Glass-making: it was obtained from iron by the late Mr. James Green, who, so far, confirmed Klaproth's analysis. The specimen of the Egyptian idol, and the lachrymatory vase found by Mr. Banks, at Thebes, in Plate 2, are of this variety. Cobalt was probably not used for Glass coloration till a much later period: the Portland Vase and the Naples Vase (Plate No. 1) have, no doubt, crude cobalt for their colouring base (of the dark rich blue); whether they are late Egyptian or Grecian manufacture, it is difficult to decide.

The foregoing and the following analysis of coloured Glasses are extracted from a work by Minutoli, published at Berlin, in 1836, entitled "Uber die Anfertigung und die Nutzanwendung der Farbigen Gläçer bei den Alten:"

This difference is conjectured to be potash or alumine. Flint Glass manufacturers produce a beautiful red from a mixture of copper and iron, and sometimes accidentally: for instance when the ordinary metal mixed specially for light green medical bottles, is nearly worked out, it will assume the complementary colour—viz., a ruby red; so that the same bottle will be parti-coloured red and green.