O P H 
fleets a splendid white, as- does the eye of a 
eat : hence the name of this stone. 
Two specimens analysed by Klaproth, the 
first from Ceylon, the other from Malabar, 
were compo ed of 
95.00 
94.50 silica 
1.75 
2.00 alumina 
1'. 50 
1.50 time 
0.25 
0.25 oxide of iron, 
98.5 
98.25 
OPATRUM, a genus of insects of the co- 
Jeoptera order ; the generic character is: an- 
tenna' moniliform, thicker towards the top; 
head projecting from a cavity in the thorax ; 
thorax a little flattened, margined; shells im- 
fnarginate, longer than the abdomen, There 
are about 28 species of this genus. 
OPERATION. See Surgery. 
OPERATIONS in chemistry. See Che- 
mistry. 
O PERCU LARIA, a genus of the class 
and order tetrandria monogynia : the flower 
is compound ; calyx common, one-leafed. 
There are three species, insignificant herbs of 
New Holland, &c. 
OPHICEPHALUS, a genus of fishes of 
the order thoracici ; the generic character is: 
head coated with dissimilar scales ; body 
elongated. 
1. Ophicephalus punctatus: length about 
ten inches ; dorsal fin commencing at no 
great distance from the head, and continued 
nearly to the tail ; it is of moderate breadth, 
and of a dusky colour spotted with black ; 
anahfin of similar shape and colour. Native 
of India, inhabiting rivers and lakes, and 
considered as a delicate and wholesome food, 
2. Ophicephalus striatus : length about 12 
inches ; shape rather longer than that of the 
preceding species. Native of India, inhabit- 
ing lakes, where it often grows to a much 
larger size than first mentioned. It is in 
equal esteein as a food with the former spe- 
cies, and even recommended as a proper 
diet for convalescents. Native name wrahl. 
There is one other species. 
OPHIDIUM, a genus of fishes of the order 
apodes ; the generic character is : head some- 
what naked ; teeth in the jaws, palate, and 
throat ; branchiostegous membrane seven- 
rayed, patulous ; body ensiform. 
1. Ophidium barbatum : the head of this 
fish is small; the upper jaw rather longer than 
the lower, and both beset with a great many 
small teeth ; the lips are strong and fleshy ; 
in the throat are several small teeth; between 
the eyes and mouth are four small pores. It 
is commonly found of the length of eight or 
nine inches, and sometimes twelve or four- 
teen; and is met with in all parts of the Me- 
diterranean sea, and in great plenty in the 
Adriatic. It is often taken by nets in Pro- 
vence and Languedoc with other kinds of 
fish, and is most common during the summer 
season. It is not considered as an elegant 
fish for the table, the flesh being rather 
coarse. It feeds on small fishes, crabs, &c. 
&c. 
The ophidium aculeatum, or prickly ophi- 
dium, inhabits the fresh rivers in India, feeds 
on worms and a fat kind of earth, is esculent 
and long. See Plate Nat. Hist. fig. 300. 
There are four species. 
OPPIIOGLOSSUM, adder's tongue, a 
genus of the natural order of Alices, in the 
OPH 
cryptogam ia class of plants. The spike is 
articulated, flat, and turned to the tw r o sides, 
with the articuli or joints opening across. 
There are nine species, of which the only re- 
markable one is the vulgatum, or common 
adder’s-tongue, which is a native ot several 
places of Britain, growing in meadows and 
moist pastures. The country-people make 
an ointment of the fresh leaves, and use it as 
a vulnerary to green wounds. 
OPHIORIIIZA, a genus of the vnonogv- 
nia order, in the pentandria class of plants, 
and in the natural method ranking under the 
47th order, stellatas. The corolla is funnel- 
shaped; the capsule twin, bilocular, and 
polyspermous. There are three species, the 
most remarkable of which is the Asiaticum, or 
true lignum colubrinum. The root of this is 
known in the East. Indies to be a specific 
against the poison of that most dreadful ani- 
mal called the hooded serpent. 
The true root is called mungus, for the 
following reason: There is a kind of weasel 
in the East Indies, called mungutia by the 
natives, mungoby the Portuguese, and mun- 
cas by the Dutch. This animal pursues the 
hooded serpent, as the cat does the mouse 
with us. As soon as the serpent appears, the 
weasel attacks him; and if she chances to be 
bitten by him, she immediately runs to find 
a certain vegetable, upon eating which she 
returns, and renews the fight. That cele- 
brated traveller Kaempfer, who kept one of 
these weasels tame, that ate with him, lived 
with him, and was his companion wherever 
he went, says he saw one of these battles 
between her and the serpent, but could not 
certainly find out what root the weasel look- 
ed out for. But whether the weasel first dis- 
covered this antidote or not, it is an infallible 
remedy against the bite of the hooded ser- 
pent. And this he undertakes to ascertain. 
OPHIONYLUM, a genus of the moncecia 
order, in the polygamia class of plants, and 
in the natural method ranking with those of 
which the order is doubtful. The herma- 
phrodite calyx is quinquefid ; the corolla 
quinquefid and funnel-shaped, with a cylin- 
drical nectarium within its mouth. There are 
two species, shrubs of the East Indies. 
OPH IRA, a genus of the monogynia or- 
der, in the octandria class of plants. The 
involucrum is bivalvular and triflorous ; the 
corolla is tetrapetalous above; the berry uni- 
locular. There is one species, a shrub of 
Africa. 
OPHITES, in church history, Christian 
heretics, so called both from the veneration 
they had for the serpent that tempted Eve, 
and the worship they paid to a real serpent. 
They pretended that the serpent was Jesus 
Christ, and that he taught men the know- 
ledge of good and evil. They distinguished 
between Jesus and Christ: Jesus they said 
was born of the Virgin, but Christ came down 
from heaven to be united with him ; Jesus 
was crucified, but Christ had left him to re- 
turn to heaven. 
OPHRYS, tzvijblade, a genus of the dian- 
dria order, in the gynandria class of plants, 
and in the natural method ranking under the 
7th order, orchidere. The nectarium is a 
little carinated below. There are 34 species ; 
but the most remarkable are the following : 
I. The ovata, oval-leaved ophrys, or com- 
mon twyblade, has a bulbous fibrated root,. 
OPT 293 
crowned by two oval, broad, obtuse, ve.ned, 
opposite leaves; an erect, succulent, green 
stalk, six or eight inches high, naked above, 
and terminated by a loose spike of greenish 
flowers, having the lip of the nectarium bifid. 
The flowers of this species resemble the figure 
of gnats. 2. The spiralis, spiral orchis, or 
triple ladies’-tresses, with a cluster of oval, 
pointed, ribbed leaves ; erect simple stalks, 
half a foot high, terminated by long spikes of 
white odoriferous flowers, hanging to one 
side, having the lip of the nectarium entire, 
and crenated. 3. The nidus-avis, or bird’s- 
nest ; with loose spikes of pale-brown flowers, 
having the lip of the nectarium bifid. 4. T he 
anthropophora. man-shaped ophrys, or man- 
orchis ; with spikes of greenish flowers, re- 
presenting the figure of a naked man : the 
lip of the nectarium linear, tripartite, with the 
middle segment longest and bifid. There is 
a variety with brownish flowers tinged with 
green. 5. The insectifera, or insect-orchis, 
has spikes of insect-shaped greenish flowers, 
having the lip of the nectarium almost fiye- 
lobed. • This wonderful species exhibits 
flowers in different varieties, that represent 
singular figures of flies, bees, and other in- 
sects, and are of different colours in the vari- 
eties. 6. The monorchis, or musky ophrys, 
with a loose spike of yellowish musky-scent- 
ed flowers. 
OPHTHALMIA. See Medicine. 
OPIUM. See Narcotic principle, 
Papaver, and Materia Medica. 
OPOBALSAMUM, or balm of Gilead, a 
resin obtained from the amvris Gileadensis, a 
tree which grows in Arabia, especially near 
Mecca. It is so much valued by the Turks, 
that it is rarely imported into Europe. Little 
is therefore known of its composition. It is 
said to be at first turbid and white, and of a 
strong aromatic smell, and of a bitter, acrid, 
astringent taste ; but by keeping, it becomes 
limpid and thin, and its colours change first 
to green, then to yellow, and at last it as- 
sumes the colour of honey. 
OPOPONAX, a resin obtained from the 
pastinaca opoponax, a plant which is a native 
of the countries round the Levant. The gum- 
resin is obtained by wounding the roots of the 
plant. The milky juice, when dried in the 
sun, constitutes the opoponax. It is in lumps 
of a reddish-yellow colour, and white within : 
taste bitter and acrid. With water it forms a 
milky solution. Its specific gravity is 1.62. 
OPOSSUM. See Didelphis. 
OPPOSITE SECTIONS, are two hyper- ■ 
polas made by cutting two opposite cones by 
the same plane. See Conic Sections. 
OPPOSITION, in astronomy, is that as- 
pect or situation of two stars or planets, 
wherein they are diametrically opposite to 
each other, or 180° asunder. 
Opposition, in geometry, the relation of 
two things, between which a line may be 
drawn perpendicular to both. 
OPTATIVE MOOD, in grammar, that 
which serves to express an ardent desire or 
wish for something. In the English language 
we have neither optative nor subjunctive 
mood. 
OPTICS,' the science which explains the 
properties of light. 
Optical definitions and principles. 
1- Light is a matter, the particles of which.. 
