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tremtties of the petals ; and, with all the caution that can be feken, the water diftilled from thefe will have but very little fmell, if the feafon chance to prove rainy. This is not the cafe in the wallnuttree flowers ; thefe contain a large quantity of effential oil, and, confequently give a very iWg-fcented water ; but this water very often vanes from the fmell of the flower, acquiring in the delation the fmell of the bitter almond : the reafon of this is, that the embryo fruit ts contained in the flowers, and it is that which is the principal fource of the oil, and the oil it yields is wholly ana- logous to the fruit of the bitter almond.

Peach bloflbms afford a very fweet-fcented water, and their young leaves have a fmell like that of bitter almonds, and in general the fame obfervation may be extended to all thofe plants which have bitter kernels in the fruit. It is obfervable, that among the radiated flowers, fuch as that of colts foot, and the like, the flower itfelf has little or no fmell, but whatever fcent we perceive in it, arifes from the cup, whole fcales, or constituent leaves, have either a velvety down, or a feries of veficles which contain all the effential oil, and, confequently, all the odour. When flowers of this kind are to be diftilled for their oil, they muff, therefore, be ufed before they are blown open, as the veficles are then in their fineft ftatc. Thefe ve- ficles are fo large and numerous in hot feafons, in the cup of the marygold, the fun-flower, and fome .other fuch plants, that they are eafily diftinguifhed by the naked eye. Balm has very little effential oil, and if it be not chofen for di- stillation in a very favourable time, its water will have fcarce any fcent at all. The moft favourable time is, when the plant is fulleft of veficles, and that ufually is when it is about fix or eMit inches high ; its leaves appearing fomewhat reddifh, and being but of about half the bignefs they are to grow to. This obfervation extends alfo to moft of the plants of the fame clafs, nay even to the woody ones, except that they are more aromatic ; that is, that they contain a number of veficles of an" odorous refin, which is wholly owing to the clofer and firmer texture of the wood.

Sage, while young, when its {talks are not yet grown woody, is all over odorous, even its ftalks, as well as every other part, being full of thefe veficles of fweet-fcented matter, which may be expreffed on preffing them. When the effential oil of fege is to be drawn, the plant is always to be chofen in this ftate, and the more woody ones which have flood through a whole feafon, are always found to have loft the greateft part of their odour in diftillation. The woody part of this plant has no fmell ; the outer bark, indeed, has fome fcent, but that very little.

The flowers of rofemary, fage, and lavender, and others of the fame kind, though in the whole they yield a very fweet fcent, yet the aromatic eifence is npt lodged in them where it might moft naturally be fuppofed ; that is, in the petals, for if we p ill thefe clean out of the cup, as in the violet and clove we ought to do, the feparated petals have very little fmell, and that little is not effential to the pe- tals, but is wholly owing to the breaking of fome of the veficles which are placed in the furrows of the cup, in which all the fmell is contained, and which, being burft in the violently drawing away the flower, leave a little of their contents on it. Indeed, if thefe cups are obferved with a microfcope, or, but attentively, by the naked eye, they will all be found full of fmall bladders, which contain a pure effential oil, of a very high and aromatic fcent. Thyme and lavender mould either have their tops cut off, and thofe diftilled immediately, or elfe they mould be gent- ly dried, and both flowers, tops, and young leaves, be di- ftilled, fince thofe are endued with a very aromatic fcent at their firft mooting.

Among the trees, very many have fweet-fcented leaves and flowers, while the wood has not the leaft odour ; to draw the oil from thefe the young {hoots are to be taken, fince the vefi- cles which contain the effential oil are all lodged in thefe, and are at this time in their belt ftate, the heat of the fun exhale- ing afterwards their moft volatile parts. Even the young wood of thefe {hoots is capable of affording fome oil, fince in it, thefe veficles are placed between the outer and the inner bark, but thefe are all perfectly deftroyed before the wood hardens ; this is the cafe in the orange tree, the myrtle, the bay, favin, and the hke.

It is to be obferved in the fweet-fcented woods, that the place where the refin is collected in greateft quantities, is in the knots from which young branches are to rife; this is very eafily obfervable in the firs and juniper. This is not, how- ever, the cafe in all the refinous woods ; for fome of thefe abound fo in refin, that their feveral woody beds, or layers, are all connected to one another by beds of refin ; as is the cafe in guatacum, in the calambac wood, and that of aloes. And this is more peculiarly remarkable in the laft ; for in the fineft wood of this kind lent from the Eaft-Indies, the woody parts are ftript away, and only thefe refinous beds arc left remaining ; and, confequently, while the coarfer and cheaper forts burn like our woods to a charcoal, this precious kind melts upon the fire like a true refin, and is the riiidl-fceuted fubftance imaginable.

In all the refinous woods, the young fnoots of the tree are to be preferred for the extraction of the effential oil This is well known to thofe who traffick largely in this way : And even the liquid balfams, of which enouo-h cannot be obtained by incifion, may be thus procured : they boil the tops of the branches, and the young fhootsj in wa- ter, and collect from the furface of that liquor, the fluid balfam which the boiling has feparated from the moots, and which cannot mix with it.

Befide the parts of trees, and plants, already mentioned,, as containing their effential tib, it is to be obferved that nature has enveloped the young eyes, or budo, with numerous cover- ings, thick fpread with the fame refinous matter, the ufe of which is to defend them from the injuries of the air, and from the feverities in particular of the winter. Some of thefe are filled with a foft and fine cottony down which enclofes both the young leaves, and young flowers, as is the cafe in the horfe chefnut; thefe are all externally covered with a number of thick and ftrong fcales, laid clofely one over an- other, and cemented down, as it were, with this re inous matter. Thefe make a covering which Ipirit of wine eafily bieaks open, by diflblving the refin, but which water cannot affect, and which, therefore, is impenetrable to rains. This re- fin has its particular refervoirs alfo in the bark of the tree into' which itrifes with the fap. The young buds, or eyes, in the black poplar are of the fame kind ; they have the fame downy fubftance for their lodgment, and the fame natural balfam, as it may well be called from its fweet fcent, for their de- fence.. When the leaves of this tree grow larger, thefe fcales fall off, and the leaves have then no more fmell. The refin* or balfam, mixing itfelf with the fap which ftill remains fomewhat aromatic.

It is not only the ftalksj the cups, and the fcaly eyes of plants, which contain their effential oils ; for even the aromatic roots are riot without their {hare of it. Rhu- barb is no aromatic rootj and yet the afliftance of glalTes will fhew many lucid fpecks in it, which are truly fmall parcels of refin ; and the florentine iris, and calamus aro- maticus, contain great numbers of fuch lucid fpecks, or parcels of pure refin.

The ftalk of angelica lias a very aromatic fmell, and the feeds have a very different one; the root alfo is very, aro- matic, its parenchyma being all filled with the veficles which contain the baifamic eflence. The plant of the elecampane has fcarce any fmell, while the root is very aromatic, al- moft all the veficles of balfam being contained there. The feat of thefe refinous, or oily particles, is ufually the whole parenchymatous fubftance of the root, efpecialty in thofe roots which have no woody fubftance in the middle ; fuch as rhubarb, and the like; and thofe which have woody matter in their middle, contain this aromatic fubftance in their bark ; fuch are the roots of fraxinella, and the like* of which we therefore ufe in medicine, only the outer bark.

Thus we have traced the feveral refervoirs of the effential oils in plants, and, as for the manner of feparating them from the fubjefts, it has been delivered above. See Effential Oil.

Oil dregs* See the article Dregs.

OISEAU, in conchyliology, the name of a peculiar fpecies of oifter, of fo remarkable a figure, that it reprefents a bird with its wings expanded, and has a fmall protuberance at the hinge, reprefenting a head, and a long procefs at the oppofite end, which very well reprefents a tail. It is of a dufky reddifh co- lour on the outfide, and of a fine pearly hue within. When the outfide of this fhcli is taken off, and it is nicely coloured, by cutting it down to a proper depth in every part, it is of a fine reddifh yellow, and is the aurora {hell of collectors.

OISTER, in zoology. See Oyster.

OKE, an Egyptian weight, confuting of three rotolos, each of twelve ounces, at twelve drachms to the ounce, and fix'teen carrats to the drachm. Pocock's Egypt, p. 178.

OKELA'S, in ./Egypt, and fome other of the Eaftern countries, are a fort of indifferent buildings round a court, and common I v appropriated to the merchants of fome particular country with their goods ; as at Cairo, there is one for the merchants of Nubia, and the black flaves, and other goods they bring with them; and another for white flaves from Georgia. Pocock's Egypt, Vol. 1. p. 37.

OK.ER, in natural hiftory. See Ochre.

OLD (Cycl.) — Ohn-works, in mining, are fuch that are either fallen in, or ftand unwrought. Houghton $ compleat Miner, in the Explanation of the Terms.

OLDENLANDIA, in the Linnaean fyftem of botany, the name of a genus of plants, the characters of which are thefe: The cup is a perianth i urn divided into four pointed fegments, which are inferted on the germen of the piftil, and re- main when the fluwer is fallen. The flower is compofed of four petals of an oval figure, fpread wide open, and twice as long as the fegments of the cup The ftamina are four Am- ple filaments. The anthers are fmall. The germen of the piftil is roundifh, and placed below the receptacle of the flower. 1 he ftyle is fimple, and of the length of the fta- mina. the ftigma has a rim round it. i he fruit is a

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