solid block or slab of marble, and the cavities
are filled up with a mosaic of small coloured
pieces; whereas in other specimens a thin
veneer of mosaic is formed, and is then
cemented upon a slab of inferior stone, or else
is cemented down piece by piece without
being previously formed into a veneer. The
Derbyshire mosaics produced, until recent
years, were scarcely worthy of the name,
being little more than a jumble of bits, placed
side by side because they differed in colour
and shape, and imbedded in cement; but
they now approach to the excellence of
Florentine mosaic or pietra dura; and some
of the works produced at Derby, Matlock,
Buxton, Bakewell, and Castleton, are really
beautiful. Chimney-pieces, table-tops, chess-
boards, panels, caskets, and ornaments,
are thus produced by a combination of British
marbles in the natural state, stained marble,
Sienna and other foreign marbles, malachite,
aventurine, shells, and glass—forming a rich
if not artistic kind of mosaic. There are not
wanting, and are not likely to be wanting,
those who can and will produce marble
mosaics, if purchasers can and will pay for
them. Three or four years ago, a German
artist, Herr Ganser. a pupil of the distinguished
sculptor, Schwanthaler, exhibited in London
a mosaic which must have called forth a vast
amount of time and patience. It was about
a yard in length, and not much less in breadth.
It represented the Gemini - Castor and Pollux
on horseback. The two naked youths were
built up with little bits of marble, varying in
tint to imitate the lights and shades of the
nude figure, the whole having more or less a
warm or reddish tinge; while the two grey
horses were represented by numerous tints of
grey and white marble.

Little bits of granite, of freestone, of
lime-stone, and of such-like building materials,
would be out of place; we should as soon
think of setting an elephant to dance on the
tight-rope, as to make a mosaic picture of such
bits. Yet, can we imagine that houses, and
terraces, and pavements, by a judicious
combination of warm-tinted, and yellow-tinted,
and blue-tinted stones, might have an effect
given to them agreeable to the eye, without
degenerating into meretricious tawdriness;
all would depend on the taste with which
this was done. Since the art of polishing
granite has become better known and more
practised, the dark varieties of this stone have
been much used to give a pleasing contrast
with stones of a lighter colour.

Little bits of clay have been formed into
mosaics since the times of the Romans
certainly—perhaps long before. We call such
mosaics by the learned names of tesselated
pavements and encaustic tiles. The red bits,
at least, in the Roman pavements, are clay;
but the majority of the pieces are formed of
stone or marble. The best and costliest
pavements (such as that still existing at the
Baths of Caracalla) were made of coloured
marbles of various kinds; but the inferior
productions, such as those occasionally dug up
into light in England and other parts of
Europe, are usually made of such coloured
stones as happened to be found in the vicinity.
As there is no easily-obtained stone having
so bright a red colour as burned clay, it was
usual to employ the last-named material for
this tint. In respect to the name, a tessera
was a cubical piece of stone or other
substance; A tessela was a smaller piece of the
same shape; and thus a pavement of small
cubical pieces came to be called a tesselated
pavement. The pavement found at
Woodchester, some years ago, had grey tesselæ of
blue lias, dark brown of gritstone, light
brown of hypiat limestone, and red of fine
brick. The tesselæ, in the rougher specimens,
had joints, exhibiting gaping vacuities, which
were filled up with cement.

When our pottery-people, or (to be more
respectful) our porcelain-manufacturers,
began to make clay pavements and slabs, they
were puzzled to decide on the best combination
of materials. One plan was to inlay tesselæ
of stone with coloured cement; another was
to inlay tesselæ of terra-cotta (baked clay)
with similar cements. But it was found that
in such combinations the tesselæ and the
cement were of unequal hardness, and that
the pavement consequently wore away into
holes. Another plan was to use tesselæ of
cement coloured with metallic oxides; and a
fourth consisted in the substitution of
bitumen for the cement. At length, the
experiments arrived at the method of
employing clay in varying degrees of softness,
and treated by very ingenious processes.

There are three methods, altogether
different, now employed in producing these
clay mosaics for pavements; we may call
them the soft, the liquid, and the dry methods.
In the soft method, clay of fine quality is
coloured in different tints; thin slabs are
formed in each colour; small cubes or other
shaped pieces are cut from each slab, and the
cubes are cemented, side by side, upon any
required ground-work. The surface of such a
mosaic would wear well, because the clay
tesselæ, after baking, would have equal
density. In the liquid method, the pavement
is built up of square tiles, instead of small
tesselæ, and each tile is made by a combination
of liquid clay with soft clay. A model
of the tile is first made in stiff clay, with the
pattern cut out to the depth of a quarter of
an inch; a mould is taken for this, having, of
course, the pattern in relievo. Stiff coloured
clay (perhaps brown) is forced into this
mould by means of a press, and there is thus
produced a damp heavy square tile with a
sunken pattern. To fill up this pattern,
liquid clay is prepared (perhaps yellow), or
clay with a honey-like consistence; this is
filled into the cavities with a trowel or knife;
and the tile, after being very slowly dried; is
scraped level and clean at the surface, baked