130 
THE PRINCIPAL FLOOR. 
sixteenth and seventeenth centuries ; and two of the specimens 
before us bear the date 1655. A smaller drinking glass, with a 
delicately executed painting in brown camaieu, furnishes an 
example of the style of monochrome practised by the Germans 
in the seventeenth century. 
Some specimens of old Dutch and French glass are also placed 
in this Case. On the upper shelf is a goblet of engraved glass, 
formerly used by Charles II. Through Sir Robert Gayer, one of 
his courtiers, it came into the possession of the Hodgson family. 
Modern Ornamental Glass. Cases 66, 68. — Before passing 
to the strictly modern examples of glass-making, attention may 
be called to a few specimens of old Bristol glass arranged on the 
upper shelves in Case 68, 
Much of the modern glass exhibited here was obtained from 
bhe Great Exhibition of 1851, and is noteworthy for its beauty 
of colour and elegance of decoration. The fine yellow on the 
specimens is produced by silver ; the yellow of the ordinary glass 
may be produced by charcoal, iron or antimony. 
Canary Yellow , or Uranium yellow, is the result of the com- 
bination of oxide of uranium with the flint glass. This glass has 
some peculiar optical properties. If we look through it the 
colour is purely yellow, but if we look at any surface of it upon 
which the light falls it appears green. This phenomenon, termed 
fluorescence, is possessed by uranium glass in common with many 
other bodies, such as a solution of sulphate of quinine, an infusion 
of horse-chestnut bark, and some varieties of fluor-spar. 
The finest reds on the vases, &c., are produced by the purple 
of Cassius, which may be regarded as a stannate of tin with a 
stannate of gold ; or by a solution of gold in a qua regia (nitro- 
hydrochloric acid). The ordinary red glass is produced by 
copper . The sub-oxide of copper (cuprous oxide) possesses a 
colouring power of remarkable intensity ; hence glass is usually 
only coated or flashed with the red material. 
Amethystine Glass is produced by the peroxide of manganese, 
and blue by means of cobalt. Green Glass is obtained by the 
use of iron, or preferably by cupric oxide. 
Many examples of flashing, or spreading one colour upon 
another over white glass, are in these Cases. By cutting down 
through those layers to different depths, a very ornamental 
appearance can be produced. 
Iridescent Glass may be prepared by heating the finished 
article in water containing hydrochloric acid, under pressure, or 
by exposing the heated glass to the vapour of stannous chloride. 
Examples of modern imitations of millefiore, and improve- 
ments on the old Venetian work are shown, and a specimen 
exhibiting the manner in which the sections of canes are dis- 
posed previously to their being enclosed in a mass of transparent 
glass, accompanies the specimens. When these coloured canes 
