Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/153

 DOS

OPE

then called by the French, thecierge, or wax-fhell. ZeeXo-

LUTA,

Onyx, in zoology, a name by which Pliny, and many other of the antient writers, have called the folen. Sec Solen.

Onyx indicus* 'in the materia medica of the atitients, a term tifed by the Greek writers to exprefs what is ufually called unguis odoratus, or the fweet hoof. Some call it mychus iv.di- cm, as particularly Myrcpfus in his antidote of fifty fpecies. The fame author mentions the blatta bizantia, and tells us that it is not the fame thing with the onyx indicus, but that the kalians called by this name thebsnafi or bone of the nofe of the purple fifh. What he means by this is probably the bony tongue of that animal, nature having given it fuch a weapon

to pierce

the dells of thofe fifh on which it is to feed. We

frequently find the chamse, and other fhell-fifh, with holes bored through the upper {hell as exact as if it were done with an inurnment : this has been done by the purple fifh, to get at the fiefh of the animal within for food ; and the bony tongue ■with which this fifh performs this, is called by the Italians of thofe times blatta Byzantia. Actuarius tranfiates the blatta Byzantia of all the earlier writers by the phrafe os nap purpura: ; and the interpreters of the Arabian writers give the fame . name to what they call unguis odoratus, or onyx indkus, for the Arabian name exactly expreffes this.

The word blatta among the earlieft Latin writers, means a bubble of mud. Paulus ^gincta quotes Feftus for many in- fiances of the word being ufed originally in this fenie : after this, it became ufed for the grumes, or clots, into which the red part of the blood concretes, after it is out of the vefl'els ; and, after this, it became a name for the fanies, or foul mat- ter, concreting in lumps, when thepurpura, or purple-fifh, was expofed to the air. The purple colour was finally called by the fame name, and from this, any thing dyed purple was fa'id to be dyed with blatta. The blatta: of the Turkifh dominions were the purple fifh of that part of the world : thefe were more excellent than thofe of any other known part, and were therefore moft employed. The word blatta Byzantia fignifics no more than purpura Byzantina, and when the purple colour had been taken out, the tongues,, or other parts of the ihells of thefe fifh, were ufed in me- dicine* under the fame name of blatta Byzantia. Thus My- repfus is found to be in the right. The onyx indkus of the Greeks was, however, very different. This, though it was alfo a fhell, or part of a fhell, was collected not at Conftantinople, but in the lakes of the Eaft-Indies. Diof- corides plainly makes it different from the purpura, by com- paring the fhell to that; he fays, it is part of a fhell fifh, in many refpects refembling the purpura. Some have fup- poied that Diofcorides underftood the whole fhell of the fifh by the word pama, which he has ufed on this occa- sion; but this is not the cafe, for the Greeks had many other wards to exprefs a fhell by, and no other author countenances the ufe of pama in that fenfe. Befides, Di- ofcorides fays afterwards, that the whole fhell of the fifh which produced the onyx being burnt, had the fame virtues with the fhell of the purpura, and other the like fifh. The Arabians feeing by this, that Diofcorides did not mean the whole fhell by this word, have expreffed his meaning by a phrafe which fignifies not a whole fhell, but a fragment, or part of one. The word pama properly fignifies oper- culum, and, as all the fhell-fifh of the buccinum kind, to which this purpura belongs, have opercula, or thin fbells, to cover the orifice when the fifh is retracted in, it is plain enough that the antients meant this by the word fama\ and this they might very well call onyx, or unguis, from its being thin, and flat, and not unaptly refembling in fize and fhapc, the human nail. This operculum, when taken from the purpura, as it feems to have been among the kofnans, who had that fifh from Conftantinople, was pro pcrly called blatta Byzantia, being the only part of the fifh ufed in medicine ; but whether this, or the bony tongue' were fo called, it is certain that this is no proper name for the true onyx indkus of the Greeks, which was not any part of the blatta, or purple fifh; but, as Diofcorides ex- prefly fays, of another fpecies of (hell- fifh, foniewhat like it. OOSCOPIA, aatrxoma, In antiquity, a fpecies of divination, wherein predictions were made from eggs. Fetter, Archaeol Grsec.1. 2. c. 14. T. 1. p. 319. DOST, in hufbandry, a name given by the people who ma- nure hops, for the kiln in which they dry them after they are picked from the ftalks. This is a fquare room, built up of brick, or ftone, ten foot wide, more or lefs, and having a door on one fide. In the midft of this room is a fire-place, about thirteen inches wide, and as much high; and, in length, reaching from the mouth fo nearly to the back part of the kiln, that a man has juft room to go round it. This fire-place is called a herfe, and the fire is let nut into the room by feveral holes in the fides, in the fame manner as in m lt-kilns. Five feet above this, is laid the floor on which the hops are to be laid to dry, and this mull have a wall round it of four feet high, to keep the hops from falling out. At one fide of the upper bed muff be made a Window by which to pulh out die hops as they

are dried into a room prepared for them. The beds mufl hi made of laths an inch fquare, placed at a quarter of an inch diftance from one another, and Gipported by beamy under- neath. The hops are to be poured on this bed with a bafket, till the whole is covered half a yard thick with them ; wheri this is done, lav them even with a take, and let a fire be made in the fire-place below. Some recommend a wood-fire, but experience fhews that nothing does fo well as charcoal ; let the fire be kept at the mouth of the furnace, for the air will be carried all the way through ; and thus let the hops lie, never ftirring them till they are thoroughly dry; when they rattle under the rake, and the inner ftalks are brittle, they are fufHciently dried, and are to be puihcd out, and a frefh parcel laid in the 00/i in their place. Some people dry their hops in a common malt-kiln, fp reading them on a hair-cloth about fix inches thick, and now and then turning them till they are all thoroughly dried, then laying them in a heap, till they are to be put in the bags. But both thefe ways are liable to fome inconvenienctes ; the bo/I generally over-drys the under ones, by the time that the per ones are dry enough; and the hair- cloth, and the turn- ing in the other way breaks and matters them, and fpills ma- ny of the feeds. See Tin-floor.

OPAL {Cyd.) — The cpal is a gem of a very peculiar kind* and has been efteemed by many, in all ages, of very great value ; though, at prefent, it is of lefs price, in propor- tion to its fize, than any other of the finer gems. The Romans efteemed it the fourth gem in value ; and its an- gularity, as well as beauty, fcem very well to entitle it to at leaft that rank; it is fofter than any other of the gems, and is with difficulty polifhed to any degree of nicety. Its moft frequent fize is between that of a pea, and a horfe- bean, but it is found as fmall as the head of a large pin, and up to the fize of a wallnut. Its figure is very vari- ous, and uncertain, but it is never found in a columnar, or cryftalliform ftate. Its moft ufual figure is an irregu- larly oblong, flatted at the bottom, and convex at the top, and dented with various fmuoiities on the fides. There have been found fome of the regular fhape of a kidney, and others almoft perfectly round, and, not unfrcquently, it is met with in thin flat pieces. It is often found loofe among the earth of mountains, fometimes on the fhores of rivers, and not unfrcquently bedded in the coarfer kinds of jafper, ten or twenty opals, of different fizes and colours, being frequently found in one ftone.

It is naturally of a fmooth furface, and fine glofs, and ma- ny of the finefr, opals that have been feen, have been worn with their native poliih. Its colour, as it appears in a fine fpecimen, is of fo mixt a nature as not to be eafily de- fcribed, but is belt expreffed by comparing it to the finefr. fort of mother of pearl. It differs, however, greatly from that in its fuperior luftre and brightnefs, and in being fo pellucid that one may fee deepjnto the ftone. As itisva- rioufly turned about, it fhews the colours of all the other gems, yellow, red, blue, green, purple, and a milky grey. The laft of thefe colours is the native dye of the ftone, and it has many of the others in a fuperior beauty even to the gems to which they naturally belong, particularly the fire- colour of the carbuncle, which feems in the opal to lie deep in the body of the ftone. It is the moft difficult to counterfeit of all the gems ; and this is done by a very fine, and well chofen piece of fome pearly fhell. It is fome- times found wanting one or more of the colours, and fome- times of a deep blueifh black, with no other colour vifible on changing the light, but a deep red, which is very ftrong and glawing, and makes it a very beautiful ftone; fometimes it has alfo a general ycllowllh caff, and fometimes a greyifh one, which greatly impair the reflexions of the other co- lours, and injure the ftone.

It is found in ./Egypt, and Arabia, arid in foms parts of the Eaft-Indies, and in Europe. The oriental ones are the fi- nefr, but thofe of Bohemia are often very beautiful. Hill's Hift of Foff. p. 600.

Counterfeit Opal. To imitate this gem in natural cryftal, ufc the following method : take yellow orpiment, and white arfenic, of each two ounces, crude antimony, and fal armo- niac, of each one ounce ; powder all thefe, and mix them well together ; put this powder into a large crucible, and lay upon it fmall fragments of cryftjl, 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 bot- tom as big as a fmall pea; when the lute is dry, fet the vef* fels 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 itfe'f; and then unlute the crucibles ; the greateft part of the cryftal will be found tinged to the colours of various gems ; not only the opal, which will be very fair, and beautiful, but the topaz, and ruby colour will be feen in others. Neri's Art of Glafs, p. 1 19- OPEN fQwf.)— &//*-Opens. See Self-#cot. OPERATION [Cyci) — Herm '/-Operation. See the article Stone.

3 OPHI-