O P A 
500 O P A 
clofing a drop of water; reflefts a {ingle colour when held 
between the eye and the light; it often cracks and be¬ 
comes decompofed by expolure to the atmofphere. Con¬ 
tains filex 98, oxyd of iron 1, alumine 1. Concerning 
the opal found in Hungary, M. Patrin fays, that,“ wherever 
they dig, the matrix of the opal is fo penetrated w'ith moi- 
■fture, that the ftones themfelves are almoft without con- 
liftency, and break between the fingers. It is only after 
feveral days, and after having been expofed to the fun, 
that they acquire all the liardnefs of -which they are lui- 
ceptible, and exhibit completely the brilliancy of their 
colours.” Caftel and Patrin’s edit, of Burton; Paris, 
1801. 
7. Opalus nobilis, real or noble opal: femi-tranfparent, 
fliining very much internally, light, hardifh, reflefting va¬ 
rious bright colours, according to its pofition as to light; 
breaking into acute fragments. Found at the foot of the 
Carpathian Mountains, and in Hungary, in folid pieces, 
and fom ** Imes incorporated into other Hones. Colour 
various, the white often reflefting a yellowifh, greenifh, 
or reddifh, effulgence, refembling a flame, when placed 
between the eye and the light. When heated, it becomes 
opaque, and is fometimes decompofed by expofure to the 
atmofphere. This fpecies is infuffble before the blow¬ 
pipe; its fpecific gravity is 2‘ii4; and its compofition is 
90 filex, and 2 of water in 100 parts ; the reft being made 
up of alumine and oxyd. From the great quantity of 
fdex that enters into its compofition, it muft appear very 
extraordinary to find the opal in the argillaceous rather 
than the iiliceous clafs of earths. 
To imitate this gem in natural cryftal, life the following 
method: Take yellow orpiment, and white arfenic, of 
each two ounces ; crude antimony, and fal ammoniac, of 
each one ounce; powder all thefe, and mix them well to- 
-gether; put this powder into a large crucible, and lay 
upon it fmall fragments of cryftal, and upon thefe other 
larger pieces of cryftal; fill up the crucible with thefe, 
and lute on to it another crucible inverted, with a hole 
at the bottom as big as a fmall pea ; when the lute is dry, 
fet thevelfel in a quantity of charcoal in a large chimney, 
covering them up with coals to the middle of the upper 
crucible ; fo long as the materials fume out at the hole, 
keep up a ftrong fire ; when that is over, let the fire go out of 
it lei f; and then unlute the crucibles. The greateft part 
of the cryftal will be found tinged to the colours of va¬ 
rious gems ; not only the opal, which will be very fair 
and beautiful, but the topaz and ruby colour will be feen 
in others. A compofition of femi-tranfparent white glafs 
and pafte, refembling the opal, may be formed by taking 
of the compofition or pafte, defcribed under Glass, ten 
pounds ; and of horn, bone, or ivory, calcined to a per¬ 
fect whitenefs, half a pound ; grind them well together, 
and fufe them with a moderate heat. See art of imitating 
geins, under the article Gem. Both thefe articles are in 
vol. viii. 
OPA'QUE, or Opake, a<lj. [opacns, Lat.] Dark; not 
tranfparent; cloudy.—Thefe dilappearing fixt ftars were 
actually extinguilhed, and turned into more opaque and 
grofs planet-like bodies. Cheyne's Phil. Prin. 
The night’s nimble net, 
That doth encompafs every opuhe ball. 
More's Life of the Soul. 
OPA'QUE, / Opacity: 
Through this opaque, of nature and of foul, 
This double night. Young's Night Thoughts. 
OPA'QUENESS,/ State of being opaque.—The earth’s 
opakenefs, enemy to light. More's Immortal, of the Soul. 
OPA'RO, an illand in the Pacific Ocean, difeovered 
by Capt. Vancouver in December 1791. Southward of 
the north-weft point, is a fmall bay with a ftrong beach, 
through wdiich there was the appearance of a conliderable 
ftream of water, falling into the fea. The fnores in moll 
parts were fo perfectly fmooth, that landing might have 
been effefted without the lead difficulty. Round to the 
north of that point is a fmall bay, in which are a fmall 
iflet and fome hocks; behind thefe, the fnore may be ap- 
.proached with great eafe at any time. The fouth ex¬ 
tremity of the illand appeared, in fome points of view, 
to form a right-angle, without the leafi: interruption in 
the fides; about half a mile to the fouth-eaft, is a fmall 
detached iflet; the Ihores are interfperled with Tandy 
beaches ; its greateft; extent, which is in a N. 18 0 W. and 
S. i8°E. direction, is about fix miles and a half, and it 
may poffibly be about eighteen in circuit. Its principal 
charafter, is a clufter of high craggy mountains, forming 
in feveral places nioft romantic pinnacles, with perpen¬ 
dicular dirt’s, nearly from their lummits to the fea; the 
vacancies between the mountains would more properly 
be termed chafms than valleys, in which there was no ap¬ 
pearance of plenty, fertility, or cultivation; they were 
chiefly clothed with Ihrubs and dwarf-trees. The tops 
of fix of the higheft hills bore the appearance of fortified 
places refembling redoubts, having a ’ fort of block- 
houfe, in the lhape of an Englilh glafs-houfe, in 
the centre of each, with rows of pallifadoes, a confi- 
derable way down the iides of the hills, nearly at equal 
diftances. Thefe overhanging buildings feemed in¬ 
tended for advanced works, and apparently capable of 
defending the citadel by a few againlta numerous boll of 
alfailants. On all of them people were obferved, as if on 
duty, conftantly moving about. Thefe buildings were 
fufliciently large to lodge a conliderable number of per- 
fons, and were the only habitations feen. Captain Van¬ 
couver faw about thirty double and flngle canoes, though 
molt of them were of the double fort; the Angle canoes 
were fupported by an outrigger on one fide, and all built 
after the falhion of thole of the Society Iflands, without 
having their very high Herns; though the Herns of fome 
of thel’e were confiderably elevated, and their bows were 
not without fome little ornament. They were very neatly 
conftrufted, though exceedingly narrow. The illand did 
not appear to afford any large timber, the broadeft planks 
of which the canoes were made not exceeding twelve 
inches. Some of the ftouteft double canoes accommo¬ 
dated thirty men ; on a moderate computation, about 
300 perfons were fuppofed to have been feen near the 
Ihip. Thefe were all adults, and apparently none exceed¬ 
ing a middle age; fo that the total number of inhabitants 
on the illand can hardly be ellimated at lefs than 1500. 
The natives appeared, notwithftanding the uncultivated 
Hate of the illand, to be exceedingly weli-fed, of middling 
ftature, extremely well-made, and, in general, their coun¬ 
tenances were open, cheerful, and llrongly marked with 
indications of hofpitality. They all had their hair cut 
fiiort, and were entirely without clothing. Although 
the cuftom of tattooing prevails fo generally with all the 
illanders of this ocean, thefe people were deftitute of arty 
fuch marks. Lat. 27. 36. S. Ion. 215. 58. E. 
OPAT'CHIN, a town of Kamtfchatka : thirty miles 
from Bolchoretllc. 
OPATO W, a town of Poland, in the palatinate of 
Sandomirz : fixteen miles weft-north-welt of Sandomirz. 
OPA'TRUM,/ in entomology, a genus of inlefts of 
the order coieoptera. Generic cliarafters—Antennae mo- 
niliform, thicker towards the tip; the head is projecting 
from a cavity in the thorax; the thorax is a little flat¬ 
tened, and margined ; Ihells emarginate, longer than the 
abdomen. There are twenty-eight fpecies fcattered over 
the globe, one of which only is common to our own coun¬ 
try, to Europe at large, and to America. They are chiefly 
found among land. 
1. Opatrum grifeum : cinereous; thorax plane ; fliells 
with three railed lines, toothed behind. It inhabits Italy. 
2. Opatrum porcatum : grey; thorax plane; Ihells 
grooved, with railed black dots between the grooves. 
It inhabits Barbary. 
3. Opatrum fkbulofum: brown; the Ihells have three 
indented raifed lines; thorax emarginate. It inhabits 
Europe 
