GEM 
of their hardness, transparency, and beanty, 
when cut and polished, are highly esteem- 
ed, and from their sm^ll size and scarcity, 
are valued at very considerable price. The 
gems have been placed among the siliceous 
fossils, as in some measure allied with 
them in external characters ; and silex was 
supposed to be their principal ingredient. 
Bergman first shewed the error of this 
opinion, and proved, by analysis, that in 
the emerald, sapphire, topaz, ruby, and hy- 
acinth, argil predominates ; their other con- 
stituent principles, as discovered by his ana- 
lysis, being silex, lime, and oxide of iron. 
Still, however, the old prejudice prevailed, 
and they have been generally ranked by 
mineralogists under the siliceous genus. 
The specific distinctions of these fossils 
were not less obscure ; they were perplex- 
ed by the distinctions of the jewellers, 
drawn from very vague notions : the colour, 
in particular, being the property in which 
the gems differ most obviously, and which 
frequently gives them their mercantile va- 
lue, served as a ground of distinction : 
hence the ruby, the sapphire, and the to- 
paz were considered as different, though 
essentially the same. Another circumstance 
added to the confusion thus introduced, was 
that, other fossils, bearing a resemblance' to 
these gems, had been classed with them ; but, 
being inferior in lustre, transparency, and 
hardness, in order to distinguish between 
them, the |epithet oriental was applied to 
those which were most perfect; and, by 
this contrivance, fossils were classed under 
one name, and regarded only as varieties of 
one species, which were totally different. 
The Oriental and the Saxon topaz, for ex- 
ample, were regarded under . this point of 
view, or as varieties of one species, to 
which the common name of topaz belong- 
ed, though they are fossils altogether dis- 
tinct. From these two circumstances, fos- 
sils were separated which ought to have 
been associated, and others were connect- 
ed, which were specifically different; and 
it has required much mineralogical discus- 
sion to disentangle the perplexity, and es- 
tablish the proper species. 
Romi de l’lsle threw the first ray of light 
on this subject, by disregarding the colour, 
and attending rather to the form of crystal- 
lization ; in consequence of which he ar- 
ranged together the principal gems named 
oriental, under the title of the oriental 
ruby. Werner also has placed them under 
one species, to which he gives the name of 
sapphire. Hauy has adopted the same ar- 
GEN 
rangement, distinguishing the species by 
the name of telesie ; and, more lately, Bour- 
non has still farther extended the relations 
of these fossils, by connecting them with 
the corundum, a fossil which had been 
brought from India, and which, analysed 
by Klaproth, was found to be composed 
principally of argillaceous earth. This, hav- 
ing in general little transparency or lustre, 
Boumon names imperfect corundum ; while 
the other variety, possessing these qualities, 
and comprising the oriental gems, is distin- 
guished by the appellation of perfect corun- 
dum : these arrangements have received the 
sanction of chemical analysis. The skill of 
Klaproth, of Vauquelin, and Chenevix, has 
been exerted in investigating the composi- 
tion of these fossils, and they have proved 
to be argil nearly pure. See Diamond, 
Corundum, Telesie, Ruby, Sapphire, 
Topaz, Amethyst, Emerald, Emery, 
Beryl, Chrysolyte, Chrysoberyll. 
GENDARMES, or Gens d’armes, in 
the French armies, a denomination given to 
a select body of horse, on account of their 
succeeding the ancient gendarmes, who were 
thus called from their being completely 
clothed in armour. 
GENDER, among grammarians, a di- 
vision of nouns, or names, to distinguish the 
two sexes. 
GENEALOGICA arbor, or tree of con- 
sanguinity, signifies a genealogy or lineage 
drawn out under the figure of a tree, with 
its root, stock, branches, &c. The ge- 
nealogical degrees are usually represented 
in circles, ranged over, under, and aside 
each other. 
GENEALOGY, an enumeration of a 
series of ancestors ; or a summary account 
of the relations and alliances of a person or 
family, both in the direct and collateral line. 
GENERAL of an army, in the art of war, 
he who commands in chief. 
A general ought to be a man of great 
courage and conduct, to have great ex- 
perience, and to be of good quality. His 
conduct appears in establishing his ma- 
gazines in convenient places ; in examining 
the country, that he may not engage his 
troops too far, while he is ignorant of the 
means of bringing them off; in subsisting 
them ; and in knowing how to take the 
most advantageous posts, either for fighting 
or shunning a battle. His experience in- 
spires his army with confidence, and an as- 
surance of victory ; and his quality, by 
creating respect, augments his authority. 
By his liberality he gets intelligence of the 
