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thefe waters ; and, among the reft, the pyrites affords a great deal of them. All kinds of die pyrites, and all the iime- ftones of England, when they are fubje£ to be much moiften- ed under around, will, in time moot out the ir falts, and part with their earths. Lifter de Font Med. Angl. The earth of the pyrites is ochre, and the fait of the lime- ftone is the calcarious nitre, an alkaline fait of the nature of the natrum of JEgypt ; and from thefe two fubftances, and a fmall portion of common fait, which the waters take up in their paffage through the earths that contain it, all the vir- tues of them are owing. The fait of the pyrites being green vitriol it might be expected that this fhould he found in the waters impregnated by that fubftance ; but Dr. Lifter obferves that though there are many fprings in England which are well known to receive their virtues from this fofiile, yet there is no fuch thine; as vitriol to he obtained from any of them ; and this is not wonderful, fince we know that the pyrites will not yield its vitriol when newly taken out of the earth, but muft be expofeu a confiderable time firft to the air; fo that the ochre only is the feniible thing that it receives from this fubftance, and, perhaps, with it fome faline matter which is the bafts of vitriol, and would be vitriol in time, on a due ex- pofition to the air. OCHROPUS gallinula, in zoology, a name by which many authors have called a bird more ufualiy known by the name of iringa. Gejrier de Avib. See the article Trinca. Ochkopus, or galUnufa Ochropus, the yelkw-leggd moorhen, a fpecies of the gallinula, or nwrhen. It is of the fize of the common kind ; its beak, as well as its legs, is yellow, or of a fulphur colour; its back is of a red i 111 brown; the tips of its wings of a very fine red ; it has white variegations on its head, and in the middle of its wings, and on its belly ; the longeft feathers of its wings are black; and there are alio fpote of black on the back in feveral places. The edges of its eye- brows arc of a deep faftron colour ; and it has, befide all thefe colours, a great deal of grey in the wings. It has no hind! toe. It builds in thickets, in watery places, among rufhes and lush grafs. Aldrovand. de Avibus, 1. 20. c. 48 Gefitrds Avib. OCHRUS, tn botany, the name of a genus of plants, the cha- racters of which are thefe. The flower is of the papilionace- ous' kind. The piftil arifes from the cup, and finally be- comes a pod, which is ufualiy of a rounded, or cylindric form, and contains a number of roundifh feeds. To this it is to be added, that the leaves are fometimes fingle, fometimes of the conjugated kind, and terminating in tendrils. The fpecies of ochrus enumerated by Mr. Tournefort, are thefe : 1. The ochrm with undivided leaves, fending out ten- drils from their ends, and with yellowifh feeds, called ervillia by fome authors. 2. The ochrus with undivided leaves, ter- minated by tendrils with brown feeds. 3. The ochrus with undivided leaves terminated by tendrils, with black feeds. And 4. The yellow-flowered, woolly, American ochrus. Tour/i. Inft. p. 396. OCIMUM, in botany. See Ocymum.

OCNUS, in zoology, a name by" which Ariftotle, and other of the antients have called the bittern, or butter bump. See the ar- ticle Bittern. OCOB, a name given by fome chemifts to fttl armoniac, OCREA, (Cycl.) among the antients, a kind of military fhoe, or ' fhort boot, which was made of white tin, and ornamented with gold, or filver, about the ankles. Its ufe was very an tient, the Greeks were fo well provided with them in Ho mer's time, that he thence gives them the appellation of E»- ' *■'*)/*&$ Ax*>"<- Among the Romans, none were allowed to wear the eerea, but the two upper clafTes of the people, or fuch whofe eftate exceeded 7500 drachms. See Hafm. Lex. Univ. tn voc. OC 1'AETERIS, "OxUimpif, in antiquity, a cycle, or term, of ■ eight years, at the end of which three entire lunar months were added This cycle was in ufe till Meton, the Athenian, reformed the calendar, by finding out the golden number, or cycle of nineteen years. Potter, Archaol. Graec. T. 1. p. 466. See Cycle, and Calendar, Cycl. OCTANDRI A, in botany, a clafs of plants with hermaphrodite flowers, and eight {lamina, or male parts in each. See Tab. 1, of Botany, Cfifs 1.

The word is formed of the Greek 3*r« eight, and «*»§ male. The plants of this clafs are the maple tree, heath, &c. OCTAVE (Cycl.) — Dimimjhed Octave, in mufic. See Di- minished oStave. OCTAV1NA, in the Italian mufic, a kind of fmall fpinnet, ea- iily moved, having only one row of keys, and thofe not to the ufual number, perhaps not to above three octaves, the com- mon ones going to four, or more. See Sp i net, Cycl. OCTOPHORUM, among the antients, a carriage with eight wheels.

It alfo fignified a chair, or litter, leifica, carried by eight chair-men, which kind of chair was moitly ufed by the wo- men. Pit'fc. in voc. OCTUNX, a word ufed by fome difpenfatory writers to fignify

ein;ht ounces. OCULATA, in zoology, a name given by many to the fifh more ufualiy called melanurus. It has the name oa/lata lrom the re-

markable largencfs, and fine golden iris of its eyes. TFillughbyS Hift. Fife. p. 310. See Melanurus. OCULATUS lapis, the eyedjlone, a name given by Mercatus, in his Metallotheca Vaticana, and by many other writers, to what we call the pudding ftone, a ftone formed of a great number of pebbles, of a fmall fize, immerfed, and formerly bedded, in a flinty cement, little lefs hard than the ftones thcmfelvcs, and in fome fpecies not at all fo. The refemblance of thefe round pebbles, when the mafs was cut, to the eyes of animals, pro- bably gave origin to this name. It is eafy to conceive that at the time when thefe ftones were formed the matter of the ce- ment was foft as mud, while the ftones which are bedded in it were hard, and perfectly formed, otherwife they could never have had admiffion into it. It is alfo natural to fuppofe, that as thefe ftones are placed very irregularly in the mafs, the ends and fides of many of them muft be prominent above the reft, and above the furface of the cement ; and this we ufualiy find to be the cafe : but in fome places we find large lumps of this ftone, whofe furfaces are naturally fmooth, as if wrought by art- the external pebbles being thus cut oft", as it were, down to the level of the furface, and their internal Ilneations appearing. We find feveral ftones rounded and fmoothed on the furface in this manner, by long lying on the ihores of the fea, and being there wafhed about among other hard bodies by the tides. But thefe ma lies are alfo found in gravel pits, and thofe fuch as have evi- dently been fo ever fince the formationof the cruft of the earth after the deluge, and have never been difturbed, or removed fince that time. As a hurry, and violent motion of the water, alone can have occafioned the wearing down of thefe peb- bles on the furface of the pudding ftone, and as they have ne- ver been in the way of fuch a motion of water fince the time of their fubfiding from among the waters of the delu<?e, it muft have been at that time that they were thus ro!Ied~a- bout, and roundeJ ; and this is one great proof of the Wood- wardian fyftem of things at that time; and that the waters, in departing from off the furface of the earth, ran with o-reat vi- olence, and carried ftones, &c. a long way in their current in which courfe they fuftcred all that the darning, and rolling a- bout in the waters of the fea, could do to fuch ftones in a long- period of time. 'See Tab. of Foflils, Clafs 5. Mercati Me- tall. Vat. p. 139. Wbodw. Cat. Foil". V0I.1. p. 46. This puddingjlone is not the only inftance of this effecT: of the rapidity of the waters of the deluge in running off" from the face of the earth, for there are found in many places great num- bers of ftones which have been parts of ftrata, or larger mafies, and which have been broken oft", and rolled into the form of pebbles at that time. And among what we common- ly underftand by the name pebbles, we find many which have prominent ridges running round them, which have been veins harder in their matter than the reft of the ftone; and there- fore, while the reft has been worn away, thefe have remained lefs worn, and confequently Handing higher than the other parts. OCULIPETA, in zoology, a fpecies of ferpents. See the article

Texmtnani- OCULUM aperient, in anatomy, a name given by feveral au- thors to a mufcle of the face, called by the generality of wri- ters aperiem palpcbra?n, and aperiens palpebrani re£lus ; by AI- binus, levator palpebra fuperioris. Oculus hsli, in natural hiftory, the name of one of the femi- pellucid gems of the genus of the bydropbarue, and called by Dr. Hill bydrophanes albidc-cinereus, jflcivo-variegatus, nucha cen- trali nigerrimo, or the greyifh white hydrophanes, variegated with yellow, and with a black, central, nucleus. See Tab ofFoffils, Clafs j.

It is a very elegant, and beautiful gem. Its bafis, or ground, is a whit if h grey, variegated with yellow, and fometimes with red, and a little black, but that more rarely, and is found in fmall mafies from half an inch to an inch in diameter ; of a rounded figure, and thickeft in the middle, tapering away gradually to the fides. The outer part of the ftone, or that toward the edges ail round, is ever of a whitiftigrey, more or lefs variegated with yellow, &c. and its central nucleus is al- ways of a deep and fine black, furrounded by a broad circle, of a pale yellow, and reprefenting very beautifully the pupit and iris of the eye; thefe are encIofi.nl in the matter of the ftone, and are often furrounded by other very fine concentric circles, of a pale flame colour ; but more frequently mere is only the black pupil, furrounded by the yellow iris, and that placed in the body of the ftone which reprefents the white of the eye : the fhape of the ftone alfo favours its refemblance of an eye, and the whole is very elegant. It is of the hardnefs of the agate, and takes a tolerable polifh ; when thrown into water, it has, in a great meafure, the property of the oculus mundi, the whole ftone becomes greatly more bright, and lu- cid, and the grey part becomes of a plainly yellowifh caft. There are many things^ improperly called oculus Belt by our jewellers, but the genuine fpecies is very rare. Nothing is more common than to find in the agates little circular veins of different colours round a central fpot ; thefe the lapidaries fre- quently cut out, with a proper quantity of the ftone about them, rind call them ocului belt. They are not peculiar to the agate, but are common alfo in the cornelian, and ftand fome-