S50 Mr Cadell on the Mmiufacture of Mosaic at Rome. 
tions ancient tiles of a kind of glass or enamel, for paving the 
doors of rooms ; and he describes a small picture composed of 
filaments of enamel of different colours, agglutinated together 
by fusion, and each transverse section of this gave a picture 
like that at the extremity. The antique pastes, or artificial 
gems, are also products of art allied to enamel. 
The Cement. — Anciently, the paste in which the pieces of 
mosaic are imbedded, called in Italy Stucco, was composed of 
-one measure of quicklime quenched in water, and three mea- 
sures of pounded marble ; these were made into a mass with 
V ater and white of egg, and this was called Marmoratum ; but 
this paste hardens too rapidly, so that it is hard before the 
workman has time to insert the pieces, and it is injured by 
damp more readily than the cement made with oil. 
The paste now used is composed of one measure of quenched 
quicklime, and three measures of powdered Travertine stone ; 
these are mixed with linseed oil, and are stirred and worked up 
43very day with a trowel. The mass is at first level on the surface, 
but afterwards swells up. Each day some oil is added, to prevent 
the mass from becoming dry and untractable. The mass is ready 
a shorter time in warm weather than in cold ; in summer the 
mass is at its perfection in twenty days ; this is known from 
its ceasing to swell, the water that was in the lime having eva- 
porated ; the mass is then uniform throughout, like an oint- 
jnent. In winter, and when the air is moist, it requires a month 
to bring the paste to perfection. 
The wall to which the mosaic is to be applied, must have the 
•lime taken off its surface.; then furrows an inch deep are form- 
ed on the wall, to fix the cement. 
For the same purpose large-headed nails are driven in, and 
wire is stretched from one nail to another. After this, the wall 
thus prepared, is painted over with linseed oil. Then the ce- 
ment is laid on to the extent of a surface of as many palms as 
can be executed before the cement dries. The plasticity and 
softness of the cement lasts about twenty days ; after that the 
oil exudes, and the lime and Travertine become a hard mass. 
The cement made with linseed oil is yellow ; that made with 
white of egg is white, and the white cement is considered to be 
a character for distinguishing the old mosaic from the modern ; 
but some of the modern is also made with white cement. 
