M O S 
take fome of the pieces of glafs, which they moiften on 
one fide with gum-water, and afterwards lay them over 
with gold-leaf: they put thefe pieces on a fire-lhovel, 
which they place in the mouth of the furnace, having firft 
covered them with another hollow piece of glafs : here 
they continue till they become red-hot; after which the 
lhovel is drawn out all at once, and the gold becomes fo 
firmly bound to the glafs, that it will never afterwards 
leave it. 
To apply thefe feveral pieces, and out of them to form 
a pifture, they firft make a cartoon, or defign ; this they 
transfer on the ground or plafter, by chalking as in paint¬ 
ing in frefco. As this plafter is to be laid thick on the 
wall, it will continue frefti and foft a confiderable time, 
fo that there may be enough prepared at once to ferve 
three or four days. This platter is compofed of lime made 
of hard ftone, with brickduft ground very fine, gum tra- 
gacanth, and w.hites of eggs: when it is thus prepared, 
and laid on the wall, and the defign finilhed of what is to 
be reprefented ; with plyers they take out the little pieces 
of glafs, ranging them one after another, and ftill keep¬ 
ing ftriCtly to the light, fliadow, and different tints and 
colours reprefented in the defign; preffing or flattening 
them down with a ruler, which ferves both to fink them 
within the ground, and to render the furface even. Thus, 
in a long time, and with an infinite deal of trouble, they 
finifh the work ; which is ftill the more beautiful, as the 
pieces of glafs are more uniform, and ranged at more 
equal heights. Some of thefe are executed with fo much 
juftnefs, that they appear as fmooth as a table of marble, 
and as finifhed and mafterly as a painting in frefco ; with 
this advantage, that they have a fine luftre, and will hold 
almoft forever. The fineft works of this kind, that have 
defcended to us, and thofe from which the moderns have 
retrieved the art, almoft loft, are thofe of the church of 
St. Agnes, formerly the Temple of Bacchus, at Rome; 
befides fome at Pifa, Florence, and other cities of Italy. 
The moft efteemed among the works of the moderns are 
thofe of Jofeph Pine, and the chevalier Lanfranc, in the 
church of St. Peter at Rome. There are fome very good 
ones likewife at Venice. 
During the prefent year (1817), without the gate of 
St. Sebaftian, near the Via Ardeatina, at Rome, in a farm 
belonging to the duchefs of Chablais, called Tor Ma- 
rancio, have been found a confiderable number of ancient 
mofaic pavements, antique paintings, and fragments of 
fculpture. Infcriptions on the leaden pipes which con¬ 
veyed the water thither, teem to indicate that this was the 
villa of the Munatia family. The pavements reprefent 
nothing but trellifes or compartments, only one of which 
difplays different colours ; the others generally are white 
or black. One of thefe pavements is very remarkable : 
upon it are feen the fhip of Ulylfes and the Syrens, one of 
whom, with birds’ feet, is playing on a lyre. In another 
part of it is reprefented Scylla, half-woman and half-fifh, 
enf lding two men with her two tails, and ftriking the 
water with a fit ip’s rudder. 
While this article was in the prefs, (Aug. 1817.) a beau¬ 
tiful piece of ancient mofaic, about twelve feet fquare, has 
been dug up in a field contiguous to Farnham in Surrey. 
2. Marble .—This kind is ufed in large works, as in 
pavements of churches, bafilics, and palaces; and in the 
jncruftation and veneering the walls of the fame edifices. 
The ground is ordinarily a mafs of marble, either white 
or black. On this ground the defign is cut with a chiflel, 
having been firft chalked. When it is dug of a fufficient 
depth, i. e. an inch or more, it is filled up with marble of 
a proper colour, firft contoured, or fafhioned to the defign 
and reduced to the thicknefs of the cavities, with various 
inftruments. To make the pieces thus inferted into the 
cavities held, whole feveral colours are to imitate thofe 
of the defign, they ufe a ftucco, compofed of lime and 
marble dull; or a maftic, which each workman prepares 
differently ; after which, the work is half polifhed with a 
loft kind of ftone. The figures thus marked out, the 
Vql. XVX No. *092. 
A I C. 53 
painter or fculptor himfelf draws with a pencil the colours 
of the figures not determined by the ground, and in the 
fame manner makes ftrokes or hatchings, in the places 
where fhadows are to be; and when he has engraved, 
with a chiflel, all the ftrokes thus drawn, he fills them up 
with a black maftic, compofed chiefly of Burgundy pitch, 
poured on hot; taking off, afterwards, what is fuperflu- 
ous, with apiece of foft ftone or brick, which, with water 
and beaten cement, takes away the maftic, polifhes the 
marble, and renders the whole fo even, that one would 
imagine it only confifted of a Angle piece ; it is this kind 
of mofaic we fee in the pompous church of the invalids 
at Paris, and the fine chapel of Verfailles ; and with which 
fome entire apartments of that palace are incrufted. 
3. Precious Stones.- —For this kind there are required 
other and more delicate inftruments than thofe ufed in 
marble ; as wheels, drills, tin plates, &c. ufed by lapida¬ 
ries and feal-engravers. As none but the richeft marbles 
and ftones enter this work, to make them go the farther, 
they are fawn into the thinneft leaves imaginable, Icarcely 
exceeding half a line in thicknefs. The block to be fawed 
is fattened firmly with cords on the bench, only raifed a 
little on a piece of wood one or two inches high. Two 
iron pins, which are on one fide the block, and which 
ferve to fallen it, ferve alfo to diredl the faw. The pieces 
to be fawed are put into a vice contrived for the purpofe : 
in which ftate, with a kind of faw or bow made of a fine 
brafs wire bent on a piece of fpringy wood, together 
with emery moiftened with water, the leaf is gradually 
fafliioned by following the ftrokes of the defign made on 
the paper, and then glued to the piece. When there are 
pieces enough falhioned to form an entire flower, or fome 
other part of the defign, they are applied. The ground, 
that fuftains this mofaic, is ufually of ftone. The matter, 
with which the ftones are joined together, is a ftucco, or 
maftic, laid very thin on the leaves as they are falhioned j 
and the leaves in this ftate are applied with plyers. If any 
contour, or fide of a leaf, be not either rounded enough* 
or fquared enough, to fit the place where it is to be ufed ; 
when it is too large, it is brought down with a brafs file or 
rafp ; and, when too fmall, is managed with a drill, and 
other lapidary inftruments. 
4. Gypfum. —Of this ftone, calcined in a kiln, beaten in 
a mortar, and palled through a fieve, they make a kind of 
artificial marbles, imitating precious ftones ; and of thefe 
they compofe a kind of moiaic work which comes little 
lhort either of the durablenefs or vivacity of the natural 
ftones ; and which has this advantage, that it admits of 
continued pieces, or paintings, of entire compartments, 
without any vifible joining. 
Some make the ground of plafter of Paris, others of free- 
ftone. If the former, it is fpread in a wooden frame, of 
the length and breadth of the intended work, and about 
an inch and a half thick. This frame is fo contrived, as 
that, the tenons being only joined to the mortifies by An¬ 
gle pins, they may be taken afunder, and the frame be 
difmounted when the plafter is dry; this frame they cover 
on one fide with a ftrong linen cloth, nailed all round; and 
being placed horizontally, with the linen at bottom, it is 
filled with plafter, palled through a wide fieve: the plafter 
being half dry, the frame is fet perpendicular, and left 
till it is quite dry, and then taken out, by difmounting 
the frame. In this mofaic, the ground is the moft im¬ 
portant part. To prepare the fifted gypfum to be applied 
on-this ground, theydiflolve and boil it in the bell Eng- 
lilh glue; and, after mixing with it the colour it is to 
bear, the whole is worked up together into the ordinary 
confiftence of plafter; and then taken and fpread on the 
ground, five or fix inches thick. It mull be obferved, 
that, if the work be fuch as that mouldings are required, 
they are formed with gouges, and other inftruments. It 
is on this plafter, thus coloured like marble or precious 
ftones, and which is to ferve as a ground to a work either 
of lapis lazuli, agate, alabafter, or the like, that the defign 
to b« reprefented is drawn; having been firft pounced, or 
P chalked. 
