‘was told by the workmen of Alexandria, that their 
Y country produced an ingredient for making coloured 
ss; and Seneca informs us, that Democritus intro- 
aced into Europe the art of making coloured glass, 
and of thus imitating the” a8 ‘stones, But from 
' whatever source this curious art was derived, it was 
. bronght to a high degree of ‘perfection among the 
Grecks and Romans; and many’of the gems were so ad- 
mirably counterfeited, as to deceive even’ those who 
were intimately acquainted with the study of minerals, 
_ In the time of Augustus, the Roman architects made 
use of glass in their mosaic decorations ; and several 
specimens of this glass have been found among the ruins’ 
a the villa of the Emperor Tiberius, in the island of Ca- 
pri. Some of these imens have been examined and’ 
analysed by Klaproth. They consist of pieces of red, 
green, and blue glass. 
th’s The first of tp of “ meer Sm ye colour, 
of perfectl e, and v right at the place of re- 
1 cent facies The ent tea as a light vettligrria co- 
lour, is opaque, and has a scoriaceous shining fracture. 
Two hundred grains consisted of 
Red Glass. Green Glass. 
ECS). aes 142, 130 grains. 
Oxide of lead 28 15 
Oxide of copper 15 20 
Oxide of iron . ey, 7 
Alumine.. ... 5 1l 
 pRincacd 2A wees 13 
a 196" 196 | 
~ The blue glass had’ a sapphire colour, verging to- 
wards that of smelt, and ‘was transparerit at the e 
only. Some of the plates of it are not coloured through- 
out the whole of their mass, but only through about 
two-thirds of their thickness. Each of the strata is so 
distinct as to give the appearance of a blue and a co- 
lourless plate adhering at their broad surfaces. 
n- A still more singular art of forming pictures with 
tres coloured glass was Acedia and practised by the an- 
colour- cients. It consists of variously coloured glass fibres, 
fitted with the utmost exactness, so that a section across 
- the fibres represents the object to be painted. These 
fibres, when properly joined together, are afterwards 
cemented by fusion into a homogeneous and solid mass; 
ae of this art seem to have been fitst discover- 
about the middle of the last century,. Count Caylus 
first describes them in his Collection of Antiquities, and 
Winkelman in his Annotations on the History of the Art 
oene ii Ancients, under the name of pictures made 
of glass tubes. Sulzer, in his Theory of the Polite 
-Arts, describes, in the article Mosaic, specimens which 
’ ~ he had seen at Dresden ; and Klaproth epics draw- 
ings of one which he has in his own possession. ‘The 
owing description of two pieces of this kind of glass, 
which were brought to Rome in 1765, is given by 
Winkelman : 
“ Each of them is not quite one inch long, and one- 
third of an inch broad. One plate exhibits, on a dark 
ground of variegated colours, a bird representing a duck 
of various very lively colours, more suitable to the Chi- 
nese arbi taste, than ed to shew the true tints 
_ of nature. The outlines are well decided and sharp, 
the colours beautiful and pare, and have a very strik- 
. 
__ ing and brilliant effect; because the artist, according to 
eee Tt ; 
* « Manifestius est, mentem esse, 
obductas.” De Opificio Dei, cap. 5. 
GLASS. 
807 
the nature of the parts, has in some employed an opaque, _ Histery. 
and in others a transparent glass. most delicate 
pencil of the miniature painter could not have traced he 
more accurately and distinctly, either the circle of the with colour- 
pupil of the eye, or the apparently scaly feathers on the ed glass, 
breast and wings, behind the beginning of which this 
iece had been broken. | But the admiration of the be- 
older is at the highest pitch, when, by turning the 
glass, he sees the same bird on the reverse, without per- 
ceiving any difference in the smallest points ; whence 
we could not but conclude, that this picture is: conti- 
nued through the whole thickness of the specimen; and: 
that, if the glass were cut transversely, the same pic- 
ture of the duck would be found repeated in the several 
slabs ; a conclusion’ which was still farther confirmed: 
by the transparent places of some beautiful colours upon 
the eye and breast that were observed. The painting 
has on both sides a granular appearance, and seems to 
have been formed, in the manner of mosaic works, of 
single pieces ; but so accurately united, that a power~ 
ful magnifying-glass was unable to discover any janc- 
tures. This circumstance, and the continuation of the 
picture throughout the whole substance, rendered it ex~: 
tremely difficult to form any direct notion of the pro- 
cess or manner of performing such a work, And the 
conception of it might have long continued enigmati- 
cal, were it not that, on the section of the fracture men- 
tioned, lines are observable, of the same colours which 
appear on the upper surface, that pervade the whole 
mass from one ite to the other; whence it became a 
rational conclusion, that this kind of painting must 
have been executed by joining variously coloured fi« 
laments of glass, and subsequently fusing the same 
into one coherent body. The other specimen is about 
the same size, and made inthe same manner. It exhi- 
bits ornamental drawings of green, white, and yellow 
colours, which are traced on a blue ground, and repre- 
sent volutes, beads, and flowers, resting on»pyramidal~ 
ly converging lines, All these are very distinct and 
separate, but so extremely small that even a keen eye - , 
finds it difficult to pursue the subtle endings, those in 
particylar in which the volutes terminate. Notwith- 
standing which, these ornaments pass uninterruptedly - 
through the whole thickness of the piece.”. 
One of the two specimens which we have mention- PLatr 
sented as in the possession of M. Klaproth, is represent~ CCLXxv. 
ed in Plate CCLXXV. Fig. 4. Both the pieces have a Fig: + 
heart-shaped form, their principal front being flat, 
and the reverse convex, The length of one of them 
is one inch, its breadth four-fifths, and its thickness, 
two-fifths. The other specimen is two-thirds of the 
size of the first; but they are botli nearly alike im 
the colouring and manner of drawing. The princi- 
pal mass of the large specimen is a/dark and _perfectly 
opaque, but the smaller one, which is in some places 
transparent, has a sapphire blue colour. The blue 
ground is ornamented ‘with voluted stellular, minute 
flowers, on such a small scale as to be scarcely imitable 
by the miniature painter. Their colours are red, green, 
brown, sky-blue, and white, and are all pure and lively. 
The delineations pervade the whole mass ; and it is ob- 
vious from examining a fracture, that those minute or- 
naments are formed'of parallel glassy fibres of various 
hues, agglutinated by fusion. 
About the end of thé 3d century, as appears from a ona 
passage in Lactantius,* Blass was: used for windows; 3). 
and there is reason to believe, from the glass plates 
Glass used 
que per oculos ea; qugesunt opposita transpiciat, quasi per fenestras lucente vitro, aut speculari tan 
