MOSAIC. 
none on the west, and ^ on tlie north. 
Tiie four outsides are filled by parallelo- 
grams and circles of considerable size, all 
divided into figures nearly similar to those 
described.” 
The above descriptions of mosaic pic- 
tures and mosaic pavements will convey a 
competent idea of the nature of the art. 
The manner in which they are composed is 
explained by Keysler, whose accuracy is al- 
most proverbial. According to this valuable 
author, persons were constantly employed 
at Rome in making copies in mosaic of those 
excellent pictures which adorned the walls 
of St. Peter’s church, to replace the latter, 
as tlie damps of the build ng were annually 
and gradually destroying tliem. The mate- 
rials used in his time were small pieces of 
glass, tinted with different gradations of co- 
lours, in the manner of the fine worsted used 
for needle work. The glass was cast in thin 
plates, and afterwards cut into pieces of 
different lengths and breadths: some of 
those intended for the composition of figures 
to be placed on vaults and ceilings were 
above half an inch in width ; but those used 
for subjects situated near the spectator 
were formed by pieces not thicker than a 
common pin, of which two millions are said 
to be necessary to compose a portrait four 
feet square. The substance prepared to 
receive these shreds of glass is a kind of 
paste, composed of calcined marble, fine 
sand, gum-tragacanth, the white of eggs, 
and oil. As some time elapses before the 
ground hardens, there is no difficulty imme- 
diately arising from the act of placing the 
glass properly, or in removing those which 
may be found misplaced ; but after a certain 
interval it becomes so extremely solid, that 
nothing less than violence has any effect 
upon it. Keysler mentions, that “ the 
paste is first spread in a frame of wood, 
which must not be less than a foot in 
breadth and thickness, if the piece be any 
thing large.” The frame is secured by 
brass nails to a plane of marble or stone ; 
and as some of the most important subjects 
are twenty feet in lengtli, and fifteen in 
breadth, an idea may be formed of their 
very great weight. The fragments of glass 
are arranged in their proper gradations in 
cases, which are placed before the artist in 
the manner that types are set before com- 
positors in printing. The former were so 
very accurate in imitating the most beauti- 
ful strokes of the pencil, that the difference, 
according to Keysler, seems to consist only 
in the colours of the copy being more vivid 
VOL. IV. 
and brilliant than those of the painting* 
When the copy is completed, they polish 
them in the same manner usual with mir- 
rors ; and after this operation is performed, 
it is almost impossible to discover that they 
are composed of an infinite number of frag- 
ments, as they rather resemble rich pictures 
covered with glass. Tliose pieces intended 
for distant view are never polished. 
The pieces of which mosaic work were 
originally formed were very large, and some- 
times gilded and silvered. About the close 
of the third century, a Florentine, named 
Andrea Tasai, contemporary with Cimabne, 
the restorer of the art of painting, intro- 
duced an improved manner of executing it, 
which soon attracted the attention of the 
rich and powerful, and in consequence mo- 
saic paintings became much more common 
than they had been for a long time before. 
Tasai, however, does not deserve the sole 
merit of reviving the art, as he acquired his 
skill from Apollonius, a Greek, who had 
performed several very fine pieces for St. 
Mark’s church at Venice. 
A few specimens of the gilded manner of 
executing figures in mosaic may still be 
seen in England, and particularly in West- 
minster Abbey, where the tombs of Edward 
the Confessor and of Henry III. have been 
adorned in this way in fanciful figures, some 
of which are perfect, but the greater part 
are destroyed by the silly practice of pick- 
ing out the fragments of glass, to discover 
what may be seen on each side — the mode 
of setting them in the cement. “ How 
mucli,” says Keysler, “ this curious art has 
been improved, during the two last centu- 
ries, may be easily seen, by comparing the 
coarse works in some of the old cupolas of 
the chapels in St. Peter’s church with the 
other pieces lately erected there. The studs 
in these old works are made of clay burnt, 
and the surface only tinctured with various 
colours.” 
Another description of mosaic work has 
been made by the moderns, in the following 
manner. That wholly of marble is done by 
preparing a piece of the same material, 
either white or black. The artist having 
traced the design upon this plane, he exca- 
vates, or cuts, it with a chisel, perhaps to 
the depth of an inch : other pieces of the 
colour necessary for the parts are then 
shaped as correctly as possible to fit the 
excavations, and set in them with cement. 
Thus far completed, the artist finishes the 
shading hy drawing interseeting lines with 
a pencil, and those being cut into the design 
Mm 
