riie colour* of the face, by artfully engaging 
the eye with somewhat of similitude in the 
back -ground to a tint in the face, which 
otherwise, in course of working to express a 
particular part, might appear too prevalent. 
In painting a head, on an oval piece of 
ivory', such as the present form of a mini- 
ature picture, draw’ the chin as nearly as pos- 
sible in the centre of the ivory, unless the 
perstn is very tall, in which case it must be 
higher up; and if very short, the contrary'. 
Mosaic painting. This w onderful branch 
of art, improperly called painting, almost de- 
fying the hand of time, has been practised in 
many countries; but the finest works of their 
kind, and those by which the moderns have 
retrieved the art, which was in a manner lost, 
are those in the church of St. Agnes, formerly 
the temple of Bacchus, at Borne, at Pisa, 
Florence, and other cities of Italy. 
The most esteemed among the works of the 
moderns are those in the church of St. Peter, 
at Rome. There are aiso very good ones at 
Venice. 
Mosaic work is composed of small pieces 
| of glass, marble, precious stones, &c. of va- 
rious colours, cemented on a ground of stucco 
or mortar, in imitation of painting. It is ge- 
} nerally employed in copying original pictures 
of the highest value in the art. 
In performing this work, it is requisite to 
provide little pit ces of glass of as many dif- 
ferent colours as can possibly be got. 
For this purpose a glass -maker's furnace be- 
! ing prepared, and the pots and crucibles full 
of the matter of which glass is made, put into 
each crucible what colour or dy e you think 
lit, always beginning with the weakest, and 
augmenting the strength of the colour from 
crucible to crucible till you come to the 
deepest tincture. 
When the glass has been thoroughly con- 
j cocted, and the colours are in their perfection, 
j take out the glass, hot as it is, and pour it on 
I a smooth marble. Hatting it down with ano- 
ther similar marble, and then cut it into slices 
of equal bigness, and about the thickness of 
an inch and a half. 
Then with an instrument, which the Italians 
call bocca dicane, you mu t make some pieces 
square, and others of different forms and 
sizes, as occasion requires. These pieces are 
to be orderly disposed in cases, as in painting 
in fresco. It is usual to range all the different 
tints in shells, and according to their colour. 
If it is desired to have gold, either in the 
’ ground of the painting, or in the ornaments 
I or draperies, take some of the pieces of glass, 
formed and cut in the manner before men- 
tioned ; moisten these on one side with gum- 
water, and afterwards lay them over with 
leaf gold; then put this piece, or several 
pieces at a time, on afire-shovel, and place it 
in' the mouth of the furnace, after you have 
first covered them with another hollow piece 
of glass. Let these stand till they are just 
red-hot, then draw the shovel out ail at once, 
and the gold will become so firmly attached 
to the glass, that it will never afterwards come 
off. 
Now in order to apply these several pieces, 
and, out of them, to form a picture, in the first 
place provide a cartoon or design, as this is 
to be transferred to the ground or plaister by 
calking, as in painting in fresco. See Fresco. 
As the plaister is to be laid thick on the 
wall, and therefore will continue fresh and 
PAINTING. 
soil tor a considerable time, there may be 
enough prepared at once to serve for as much 
work as will take up three or four days. 
This plaister i? composed of lime 'made of 
hard stone, with brickdust very line, gum 
tragacanth, and whites of eggs; and having 
been thus prepared and laid on the wall, and 
the design of what is to be represented trans- 
ferred to it, take out the little pieces of glass 
with a pair of plyers, and range them one after 
another, still keeping strictly to the light, 
shadow, different tints and colours which are 
to be represented ; pressing or Hatting them 
down with a ruler, which serves botli to sink 
them within the ground, and to render the sur- 
face even. 
A long time and tedious labour are re- 
quisite to finish the work, which will be more 
beautiful as tiie pieces of glass are more uni- 
form and ranged at an even height. 
Pi eces of mosaic 'work performed with 
exactness appear as smooth as a table of mar- 
ble, and a 3 finished and masterly as a painting 
in fresco, with this advantage, that they have 
a fine lustre and will last for ages. 
Mosaic work of marble, and precious stones, 
These two kinds of mosaic bear so near a 
resemblance to each other, as to the manner 
of working, that, to avoid repetition, we shall 
give them both under one, taking notice as 
we proceed, wherein the one differs from the 
other, either in the sawing or the ranging of 
the stones. 
Mosaic work of marble is used in large 
works, as in pavements of churches and 
palace's, and in the incrustation and veneering 
of the walls of edifices of the same kind 
Mosaic of precious stones is only used in 
small works, as ornaments for altar-pieces, 
tables for cabinets, &c. on account of the ex- 
ceeding price of the materials. 
Process of mosaic painting. 
The ground of mosaic works wholly mar- 
ble, is usually a massive marble, either white 
or black. 
On this ground the design is cut with a 
chisel, after it has been first calked. 
After it has been cut of a considerable 
depth, i. e. an inch or more, the cavities are 
filled up with marble of a proper colour, (first 
selected according to the colours of the de- 
sign, or original picture to be copied,) and 
reduced to the, thickness of the indentures 
with various instruments. 
To make t he pieces thus inserted into the 
indentures cleave fast, (whose several colours 
are to imitate the tints of the original design,) 
a stucco is composed of lime and marble-dust, 
or a kind ot mastic, which is prepared by each 
workman after a different manner peculiar to 
himself. 
The figures being marked out, the painter 
or sculptor himself draws with a pencil the 
colours of the figures not determined by the 
ground, and in the same manner makes strokes 
or hatchings in the place where shadows are 
to be ; and after he lias engraven with the 
chisel all the strokes thus drawn, he fills them 
up with a black mastic, composed partly of 
Burgundy pitch poured on hot, taking off 
afterwards what is superfluous with a piece of 
soft stone or brick, which, together with water 
and beaten cement, takes away the mastic, 
polishes the marble, and renders the whole so 
even that one would imagine it only consisted 
of one piece. 
311 
'I his is tlie kind of mosaic work that is seen 
in the church or the Invalids in Paris, and the 
chapel at Versailles, and with which some en- 
tire apartments of that palace are incrustated. 
As tor mosaic work of precious stones, other 
and finer instruments are required than those 
used in marble, as drills, wheels, &c. used by 
lapidaries, and engravers on stone. 
As none but the richest marbles and stones 
are used in this work, to make them go the 
further they are sawn into the thinnest slices 
or coats imaginable, scarce exceeding half a 
line in thickness: die block to be sawn is 
fastened firmly with cords on the bench, and 
only raised a little on a piece of wood one or 
two inches high. 
I wo iron pins, which are on one side o 
the block, and which serve to fasten it, are put 
into a vice contrived for the purpose; and 
with a kind of saw or bow, made of line brass 
wire bent on a piece of spungy wood, to- 
gether with emery steeped in water, the slice 
is gradually fashioned by following the stroke 
of the design made on paper and glued on the 
piece. 
When there are pieces enough fastened to 
form any one entire part ot the design, they 
are applied to the ground. 
The ground which supports tills mosaic- 
work is usually of free- stone. 
'Fhe matter with which the stones are joined 
together is a mastic, or a kind of stucco, laid 
very thin on the slices of marble, &c. as they 
are fashioned; this being done, the slices are 
applied with plyers; and if in any part they 
are not either squared or rounded sufficiently, 
so as to fit the place exactly into which they 
are to be inserted, they are brought down, 
when too large, with a brass file' of rasp ; and 
when too little, a drill, and other instruments 
used by lapidaries, are used to supply the de- 
ficient part. 
Manner of performing mosaic work of 
gypsum. 
Gypsum is a kind of coarse talc, or a shin- 
ing transparent stone, found in the quarries of 
Mont-Martre, near Paris, it is different from 
the plaister of Paris, but retains the name 
which the Romans gave to the plaister, viz. 
gypsum. 
Of this gypsum, or stone calcined in a kiln, 
and beaten in a mortar, and silted, the French 
have made a sort of artificial marbles, imitat- 
ing precious stones, and of these thev compose 
a kind of mosaic work, which does' not come 
far sho: t either of the durabteness or the 
vivacity of the natural stones ; and which, be- 
sides, has this advantage, that it admits ot con- 
tinued pieces or paintings of entire compart- 
ments without any visible joining. 
Some make the ground of plaister of Paris, 
others of free-stone. If it is of plaister of 
Paris, they spread it in a wooden frame, of the 
length and breadth of the work intended, and 
in thickness about an inch and a half. 
This frame is so contrived that the tenons 
being only joined to the mortises by single 
pins, they may be taken asunder, and the 
frame be dismounted, when the plaister is dry. 
The frame is covered on one side with a 
strong linen cloth, nailed all round, which be- 
ing placed horizontally with the linen at the 
bottom, is filled with plaister passed through 
a wide sieve. 
When the plaister is half-dry, the frame is 
set up perpendicularly, and leit till it i,s quit® 
