In art, the word Gem is the general term for precious stones when
engraved with designs, whether adapted for sealing ([Greek: sphragis],
_sigillum_, _intaglio_), or mainly for artistic effect (_imagines
ectypae_, _cameo_). They exist in a very large number of undoubtedly
genuine old examples, extending from the mists of Babylonian antiquity
to the decline of Roman civilization, and again starting with a new, but
less original impulse on the revival of art. Apart from workmanship they
possess the charms of colour deep, rich, and varied, of material
unequalled for its endurance, and of scarcity, which in many instances
has been enhanced by the remoteness of the lands whence they came or the
fortuity of their occurrence. These qualities united within the small
compass of a gem were precisely such as were required in a seal as a
thing of constant use, so inalienable in its possession as to become
naturally a personal ornament and an attractive medium of artistic
skill, no less than the centre of traditions or of religious and
legendary associations. As regards the nations of classical antiquity,
all seals are classed as gems, though in many cases the material is not
such as would strictly come under that heading, and precious stones in
the modern sense are hardly known to occur. On the other hand it must
not be supposed that gems engraved in intaglio were necessarily employed
as seals. At all periods many intaglios are found which could not have
been so employed without great difficulty. In Greece and Rome, within
historic times, gems were worn engraved with designs to show that the
bearer was an adherent of a particular worship, the follower of a
certain philosopher, or the attached subject of an emperor. However,
speaking generally, the intaglio engraving is a means to an end, namely,
a seal-impression, while an engraving in relief is complete in itself.
_Methods of Engraving_ (see also under LAPIDARY).--In gem-engraving the
principal modern implement is a wheel or minute copper disk, driven in
the manner of a lathe, and moistened with olive oil mixed with emery or
diamond dust. There is no clear proof of the use among the ancients of a
wheel mounted lathewise, but we have abundant indications of drilling
with a revolving tool, which might be either a tubular drill making a
ring-like depression, a pointed tool making a cup-like sinking, or a
small wheel with a cutting edge, making a boat-shaped depression.
We have one sepulchral monument from Philadelphia showing the tool of an
intaglio engraver ([Greek: daktylokoilogyphos]; see _Athenische
Mitteilungen des Arch. Inst._ xv. p. 333). Unfortunately the relief is
incomplete, and the published illustration inadequate. It would seem,
however, that a revolving tool was supported by a kind of mandrel, and
actuated in primitive fashion by a bow. An alternative plan of working
was to use a splinter of diamond set in a handle and applied like a
graver. Both systems are clearly indicated by Pliny, who in one passage
(_H.N._ xxxvii. 60) states that diamond splinters are sought out by gem
engravers and set in iron, and so easily hollow out stones of any degree
of hardness; while elsewhere (_H.N._ xxxvii. 200) he speaks of the
special efficacy of the _fervor terebrarum_, the vehement action of
drills. A third method is also indicated by Pliny (_ibid._) when he
speaks of the use of a blunted tool, which must have been moistened and
supplied with emery of Naxos.
A four-sided pendant of the Hellenistic period published by Furtwängler
(_Antike Gemmen, Gesch._ p. 400) shows clearly the successive stages of
the operation. On side a the subject is slightly sketched in with the
diamond point. On side b the deepest parts of the figure have also been
roughly scooped out with the wheel. On sides c and d the wheel work is
fairly complete, but the finer internal work has not been begun.
After the design had been completed the stone must have received a final
polish on its surface, to obliterate any erroneous strokes of the first
sketch; but this process was not carried as far as in modern work. It is
a popular error to suppose that a high degree of internal polish is a
proof of antiquity. If the interior of the design has a high degree of
polish it may be either ancient or modern, or it may be an ancient stone
repolished in modern times. If it has a matt surface uniformly produced
by intention, it is probably modern. If the design is slightly dimmed
and worn or scratched the stone may be antique, but is not necessarily
so, since modern engravers have observed this peculiarity, and have
imitated it with a success which, were there no other grounds of
suspicion, might escape detection.
_History._--It has been a subject of controversy whether the first
infancy of the art was passed in Egypt or in Babylonia, but it seems
highly probable that it was developed in Babylonia, whence at any rate
the oldest examples of engraved gems at present known are obtained. It
does not necessarily follow, however, that Egypt was therefore a pupil.
It may well be that the art was developed independently in the two
countries, although certain points of possible contact in respect of the
forms employed will be described below in the section dealing with
primitive Egypt.
_Babylonia._--At a very remote period the cylindrical form of stone was
introduced and became the approved shape, while the technical skill of
the artist was still slight, and the traces of the tools employed (drill
and pencil point) were still unconcealed.
The cylinder was suspended by a string and used as a seal. Impressions
of cylinders are frequent on contract tablets. If one of the parties
cannot use a seal he makes a nail-mark in lieu thereof, as is recorded
in the document.
But from a time that was still comparatively early the engravers could
work with considerable skill in the hard stone. In particular a cylinder
may be quoted in the de Clercq Collection bearing the name of Sargon I.
of Agade, who is placed about 3500 B.C. The cylinder is engraved with
the king's name and titles and two symmetrically disposed renderings of
Izdubar, with a vase of flowing water giving drink to a bull. The whole
is treated in a conventionalized style that indicates long traditions.
An important early cylinder in the British Museum is inscribed with the
name of a viceroy of Ur-Gur, king of Ur (about 2500 B.C.). The engraving
shows Ur-Gur being led into the presence of Sin, the moon-god.
The cylinder seal was adopted by the Assyrians, and so was carried on
continuously till the time of the Persian conquest of Babylon (538
B.C.). Meanwhile, as an alternative form the conoidal seal, rounded at
the top and having a flat base for the intaglio, came into use beside
the cylinder.
In style the Assyrians carried on the Babylonian tradition, but with no
freedom of design. Subjects and treatment became rigidly conventional.
[Illustration: PLATE I.