THE TROPICAL AGRICULTURIST 
[July i, 1891. 
PEOJFESSOB. MIDDLETON ON ANCIENT 
GEMS.* 
"Gema,” in oommon speech, means a precious 
stone, especially when engraved for an ornament 
or other purpose. This, pulling aside its primary 
meaning of a “ bud,” is pretty nearly its significance 
in olasdeal Latin, though in both languages it 
might be loosely extended to comprise a pearl. 
As used by Professor Middleton in this admirable 
manual, it bus of necessity a somewhat wider 
signifiaanoe, taking in certain materials other than 
the mauy varieties of precious stones. It includes 
for instance, Egyptian scarabs, which are often 
made out of clay or sieatUe (a variety of talc), 
Hittite "gems,” for which limestone and marble, 
among other materials, wore used, Pl teuician 
scarabs, and the mutaleignels found in the Myoei.» 
tombs. Xbose are cunous and interesting, and 
some exhibit delicate workmanship and, occasionally, 
great artistic skill. S'lll, the most attractive part 
of Professor Middleton's subject is that which is 
concerned with the gem proper, and that as it 
was handled by Greek or Koman artists. Prooious 
stones have always been the moat faeciuating of 
human posEGsaions. Their intrinsic beauty goes 
lor something ; their durability lor more. The 
imagination is fired when wo know that the article 
one touches is exactly the same as it presented 
itself to human eyes and hands thousands of years 
ago; and the feeling is intensified when art has 
added to the precious material, in the design, the 
name of the owner, or it may bo of the engraver, 
a distinct human interest. 
When we talk of precious stones, however, it 
must bo remembered that the minerals of which 
the vast majority of the finest antique engiaved 
gems are mude are by no means rare or oostly. 
The diamoud, for inetanoa, though it ooouie in 
ancient art, occurs only iu its natural crystal, the 
art of working it not having en discovered till 
comparatively recent times. tThe “diammd” of 
the High Prieet’s breast-plate was possibly a white 
sapphire. The minerals used belong in tfio main 
to a single species known as quanz, and consisting 
of silica, the oxide of u uou-molallio element ua led 
silicon. Of thbsesilioiousstonis there are numberless 
varieties, differiug fr.m one another in texture and 
colour, and through the presence in small quunlities 
of aoiesaory or intruding materials. Colourless 
rook crystal is the fundamental type of the specks. 
Ametlijst differs from it only in its colour, which 
is generally violet, but someiiraes eitrino, and its 
cun. us purqui tied structure. Among the translu- 
oont varieiies of quanz are the surd, ol whi h 
Profi Bsor Middleton remarks that “it is the luosi 
beautiful material oomiu.nly used fur anci. nt en- 
graved gems," a stone amber-coloured, red, or 
ledish-brown ; the less translucmt oorni lian 
(Prufeseor Mkidlolon always oaks it caruoliau, 
erroneously, we cannot but think/, chalcedony, 
which is milky or bluish, tho apple-green obryeo- 
prase, and the leaf-green plasma. Jasper, of whioli 
there are many varieties, and which is of very 
commou occurrence, is almost opaque. Another 
very common stone is ihe onyx, which is made 
uu of two or more bands of strata, varying in 
trauslucoucy and hue; when one of those stratis 
oons.aia of sard, it is called a sardonyx. Tha'. 
sardonyx is peculiarly interesting from its frequent 
mention in clasaioal writers. Plaio speaks of r, 
though, aa Professor Middleton tells us, it does 
not often oocut in Greek gems. The Homans 
used it largely, following the fashion set by 
jhe elder Soipio Afrioanus. A mong non sjlieinns 
•T/ie A'nyrabcd Gemnof (Hiisnical Times. J, H nrs 
Middleton. Ciunbridgo; The Huivorsity Pross-ldW. 
stones are tha ohrysoberyl, the topaz, the emerald, 
the almandine and other garnets, the peridot, 
the turquoise, the opal, and the lapis lazuli (the 
snppirwi ol Pliny the elder), — and these, from 
tho peridot onwards, are softer than quartz, or 
even than ancient paste or glass. It must be 
remembered that, for artistic purposes, the most 
transparent substanooa, whatever their intrinsio 
charms, arc not necessarily the most beautiful. 
It is the tranilucmt stones, such as sard and 
chalcedony, that are more suitable. Through these, 
light, but not the forma of objeots, oan be discerned, 
and so they reveal tha charms of fine and noble 
workmanship more then do the perteotly clear 
beryl and rock. crystal. In the farmer, the light 
passes less ttgulatly — that is, with more scattering 
of the rays — than is the case with transparent 
stones, and thus the design seems to bo illuminated 
from within. On the other hand, tho opaque 
substances ace less suitable for the purpose. Even 
such stones ss the heliotrope and the turquoise, 
wliioh are capable, when in thin epli 'iters, of 
transmitting a little light, produce an effect other 
and more pleasing than do the perfectly opaque 
materials. Some of the inoident light plunges a 
little way below the surfaeo of the gem, and lights 
up its superfioial layer. 
Precious at nos, like all oilier things of value, 
have been imitated. So we fiud that many “gems,” 
aa it will be still convenient to call them, have 
been wrought or reproduced in paste and glass. 
Paste was a bard glass coloured by various 
metallic oxides, such aa those ol manganese, 
iron, eopper, and cobalt. Sometimes a pieee "f 
paste was treated by the gem-oograver just aa if 
It were a natural stone, and sculptured by the 
aid of the same tools ; but more generally the 
glass was molted and pressed imo a mould. Such 
a moul i had boon taken from an engraved ge m 
by a pellet of elay which was afterwards hardened 
by fire. Paste-gems are often of gruut beauty in 
colour 'and design, though tue material laoks some 
thiug of the optioai propenica which disfibguish 
not a few of the true natural stones. 
The tools aud processes employed in ancient 
times in engraving gems are virtually the same 
as those in use today. Tho tools were five in 
number. The drill worked by a bow was tho 
chief. It varied in size, was made of bronze, and 
acted in virtue of the emery or ooruadum powder 
(mixed with oil) with which its point was smeared. 
The drill was occasionally tubular; in that case 
its crovve was sometimes set wiih small crystals 
of ooruudura. The seoond tool was a wire- 
saw, made tffective with the same abrading material. 
The wheel, or duo of bronze, was aiinitaily employed. 
A file was also used, not of meial, but of a mix- 
ture of emery aud rosin, hi at d together, and 
than allowed to solidify by eooliug. The fifth tool 
was a graver, made by mounting in an iron or 
bronze handle a crystal or crystalline fragment of 
diamond or ol sapphire, or sometimes a piece ol 
rock-crystal. As a rule, in engraving antique gems, 
and also those of the cinque-oeuto lime, the tool 
used was worked by the hand, tho atone to bo 
engraved being fixed. In more recent days, the 
reverse arr.ingomsnt is fokowed, and in oonsequenoe 
the touch is less free and the style more meohanioal. 
The Ol, graved work and the field of gems wore 
p dished by rubbing them with fine powd, ra, 
bioinatite, or red oxide of iron, having been generally 
employed for ihia purpose. 
Paste was often 1, gitimately used, but it naturally 
suggests the subj-oi of fraud. Ihe anoienta were 
nut inexpert lu this branch r,f art, if it may be 
co called. One might say that the pair of green 
glass pillars in tho temple of tho Tyrian Heioulea 
