Gazometer which was the ordinary 
os 
—\— 
Engraved 
gems. 
Substances 
chosen, 
GEM 
price of the first newspaper 
printed in that city. The first Gazette is said to have 
been published at Paris in 1631. The. first English 
Gazette appeared at Oxford on November 7, 1665, in a 
folio half sheet. When the court removed to London, 
it was called the London Gazette. 
~GAZOMETER. See Cuemisrry, p. 155; and Gas 
Licuts. ' 
- GELATINE.. See Cuemisrry, p. 130. 
GEMS. This appellation is employed in two differ- 
ent senses: first, in denoting jewels or precious stones, 
which, from rarity and beauty, have always been high- 
ly prized by mankind ; secondly, in characterizing stones, 
which, though not of the former description, are sculp- 
tured or engraved with various subjects, and more es- 
pecially if executed by the ancients. But the name of 
gems is likewise applied, in a less appropriate significa- 
tion, to artificial compositions designed to imitate the 
finer precious stones, either when polished ‘in the natural 
state, or when they have passed through the hands of 
the engraver. In our article Minrraoay, we shall 
have occasion to consider the subject of precious stones 
at some length, and we shall at present confine our at- 
tention to the subject of Engraved Gems. 
It is probable that no stone of sufficient hardness was 
excluded from receiving the engravings of the ancients; 
but it has been doubted whether they were acquainted 
with the means of cutting the diamond, or sculpturing 
the emerald and topaz. Much difference is experienced 
in working hard stones: the emerald is only to be con- 
quered by uncommon patience, and a long time is re- 
guisite to produce a.good engraving. The Eastern na- 
tions are unacquainted with the proper method of cut- 
ting and polishing the diamond ; and it is said that little 
more than a century has elapsed since the means of dis- 
posing its lustre to the greatest advantage in brilliants 
was discovered, The ancient Jews, in the days.of Aa- 
ron, according to Scripture, could engrave on dia- 
monds ; and if the same art was unknown to the Greeks 
or Romans, they were sufficiently acquainted with the 
use of this stone in cutting other jewels. But if we 
consider the ingenuity of the Greeks and Romans, it 
is not unreasonable to conclude, that they frequently 
engraved on precious stones. There are indeed few 
instances of the fact: thousands of their works must 
have perished many centuries ago, and many are still 
to be brought to light. Yet it is affirmed, that the art 
of polishing the diamond, as it now. appears, is not of 
anterior date to. the year 1456, and that engravings 
upon it belong exclusively to the moderns, having been 
attempted only about the succeeding century. In the 
year 1500, Ambrose Caradosso, an Italian, engraved 
the portrait of a father of the church on a diamond, 
which he sold to Pope Julius II. a great patron of the 
arts, for £5500, an immense sum at that period. His 
example was followed by subsequent artists, and dia- 
mond dust was used in reducing this gem itself. 
The substances most frequently sculptured by engra- 
vers, both ancient and 9, vy are rock crystal of dif- 
ferent colours, jasper, calcedony, cornelian, onyx, blood 
stone. Rock crystal, which is well known, is not consi- 
dered of sufficient hardness, and the same has been ob- 
served of malachite, which is also sometimes used. 
Jasper is found in great, variety, as well in appearance 
as quality, and in pieces of large dimensions ; none but 
the finest and most compact is employed; and this oc- 
curs both in the colder and warmer climates. Cor- 
nelian and calcedony are so nearly allied, that their 
names are mutually interchanged according to the tinge 
which either exhibits ; but the latter, which is also cals 
124, 
GEM 
led white cornelian by lapidaries, is to be distinguish- 
ed by a greyish-white colour, ing marks which 
resemble the scoopings of a knife on wood, and occa= 
sionally exhibiting a sky-blue colour. The ancients 
are supposed te have obtained the best species by the 
route of Carthage, from the mountains of st ind 
menes in Africa, and also from Thebes. One of their 
most favourite stones was the cornelian, on which all the 
ingenuity of their art has been anxiously bestowed: its. 
colour, hardness, and texture, are the most favourable 
for delicate engravings, and it seems to have been diffa- 
sed in much greater abundance than any other. This 
stone is seen of differerit shades, from’ cherry red to 
flesh colour, and sometimes of a yellowish tinge, or 
brownish colour; but exposed to moderate heat it be- 
comes white. The ancients divided it into two spe- 
cies, male and female, the latter being pale yellow:; and 
they obtained both from India, Arabia, and other parts 
of Asia, as well as the Mediterranean islands, At pre= 
sent the finest cornelians come from the east, - 
larly the Indian peninsula, where they are found from 
the size of a nut to several inches in diameter, and con- 
stitute a considerable article of traffic: the Dutch also 
brought a quantity from Japan, during the subsist- 
ence of their trade with that island. A large propor. 
tion of ancient and modern engravings are executed on 
beautiful cornelian, the colour of which may be deep- 
ened and improved by the proper application of heat, 
The onyx has been esteemed valuable since the ear- 
liest periods of Jewish history, from the singular com- 
bination of its colours ; and it was equally prized by the 
Greeks and Romans, who applied it to their most va- 
luable works of art. This stone is considered a calce« 
dony, the colours of which are disposed in alternate 
zones or strata. Generally they do not exceed two or 
three ; five or six are extremely rare. The proper 
gems of onyx consist of parallel zones, as these only 
can be worked to advantage ; but there are other two 
varieties with undulated zones, or concentric nuclei, 
resembling the eye of animals. Where the stripes are 
of various colours, lapidaries commonly call the stone a 
sardonyx, a vague and indefinite appellation, and used 
in another sense by mineralogists, But some appl 
the name of sardonyx where the ground is peti 
and that of onyx where it is white. It is not known 
where the latter was obtained by the ancients, but it 
is now found principally in Germany and Scotland. 
Artists have ingeniously disposed of the combination, 
articularly in sculpturing cameog or figures in res 
ief : a white subject appears on a dark ground; or 
if there be three colours, the third is artfully con- 
verted to drapery, or some accessory of the general 
design. This may be easily understood on reflect« 
ing, that the thickness of each zone is worked so as 
to leave one surface entire, or penetrating still deeper, 
the artist avails himself of two. M. Mariette speaks of 
a of this kind, consisting of four equidistant zones 
of different colours, describing four ellipses within each 
other in as great perfection as if drawn mathematically ; 
and in the centre was engraved a small figure of a Bac« 
chante adapting his footsteps to the sound of his lyre, as 
if it had been a picture fitted into a frame. The i ; 
onyx said to exist, is an oval of eleven inches by nine,, 
on which is sculptured the apotheosis of Augustus in. 
four zones, two of which are brown and the others 
white. Several stones of the same species have attracted. 
the particular notice of antiquarians : such is the Bruns~ 
wick vase six inches in height, representing Ceres in 
quest of Proserpine ;. Venus on a marine animalsurround~ 
ed by Cupids, engraved upon an onyx of two zones > 
a eee ae 
