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· firs, whose oil being in greater quantity, and more tenacious of the acid fpirit or vegetable soul (as perhaps it may not improperly be called) abides the action of the sun, and attracting the fun beams, is thereby exalted and enriched, so as to become a most noble medicire ; such is the last product of a tree, perfectly maturated by time and sun.

39. It is remarked by Theophrastus, that all plants and trees while they put forth have most humour, but when they have cealed to germinate and bear, then the humour is strongest and most sheweth the nature of the plant, and that, therefore, trees yielding resin should be cut after germination. It seems also very reasonable to fup. pose the juice of old trees, whose organs bring no new fap, should be better ripened than that of others.

40. The aromatic flavours of vegetables seem to depend upon the sun's light, as much as colours. As in the production of the later, the reflecting powers of the object, so in that of the former, the attractive and organical powers of the plant co-operate with the fun (a). And as from Sir Isaac Newton's experiments it appears, that all colours are virtually in the white light of the sun,

and shew themselves when the rays are separated · by the attracting and repelling powers of objects,

even to the specific qualities of the elaborate juices of plants, seem to be virtually or eminently contain. ed in the solar light, and are actually exhibited upon the reparation of the rays, by the peculiar powers of the capillary organs in vegetables, attracting and imbibing certain rays, which produce certain flavours and qualities, in like manner as certain rays, being reflected, produce certain colours.

(a) 36, 37.

41. It 41. It hạth been observed by some curious anatomists, that the secretory vessels in the glands of animal bodies are lined with a fine down, which in different glands is of different colours. And it is thought, that each particular down, being originally imbued with it's own proper juice, attracts none but that sort ; by which means so many vari. ous juices are secreted in different parts of the body. And perhaps there may be something analogous to this, in the fine absorbent vessels of plants, which may co-operate towards producing that endless variety of juices, elaborated in plants from the same earth and air.

42. The balsam or effential oil of vegetables, contains a spirit, wherein consist the specific qualities, the smell and taste of the plant. Boerhaave holds the native presiding spirit to be neither oil, falt, earth, or water ; but somewhat too fine and subtile to be caught alone and rendered visible to the eye. This when suffered to fly off, for inftance, from the oil of rosemary, leaves it destitute of all favour. This spark of life, this spirit or soul, if we may so say, of the vegetable departs without any sensible diminution of the oil or water wherein it was lodged.

43. It should seem that the forms, souls, or principles of vegetable life, fubfift in the light or solar emanation (a), which in respect of the macrocosm is what the animal fpiric is to the macrocosm; the interior tegument, the subcile instrument and vehicle of power. No wonder then that the ens primum or scintilla spirituosa, as it is called, of plants should be a thing so fine and fugacious as to escape our nicest search. It is evident that nature at the sun's approach vegetates ; and

(a) 40.

languishes

languishes at his recess ; this terrestrial globe seeming only a inatrix disposed and prepared to receive life froin his light ; whence Homer in his hymns stileth earth the wife of heaven, ä roxi ougars asegóevlos..,

44. The luminous spirit which is the form or life of a plant, from whence it's differences and properties fow, is somewhat extremely volatile. It is not the oil, but a thing more fubtile, whereof oil is the vehicle, which retains it from flying off, °and is lodged in several parts of the plant, particularly in the cells of the bark and in the feeds. This oil purified and exalted by the organical powers of the plant, and agitated by warmth, becomes a proper receptacle of the spirit ; part of which fpirit exhales through the leaves and flowers, and part is arrested by this unctuous humour that detains it in the plant. It is to be noted this essential oil animated, as one may fay, with the flavour of the plant, is very different from any fpirit, that can be procured from the same plant by fermientation,

45. Light impregnates air (a), air, impregnates vapour ; and this becomes a watery juice by diftillation having risen first in the cold still with a kindly gentle heat. This fragrant vegetable water is poffeffed of the specific odour and taste of the plant. It is remarked that distilled oils added to water for counterfeiting the vegetable water can never equal it, artificial chemistry falling short of the natural.

46. The less violence is used to nature the better it's produce. The juice of olives or grapes is. fuing by the lightest pressure is best. Resins that drop from the branches spontaneously, or ooze upon the fightest incision, are the finest and most

(a) 37. 43.

fragrant.

fragrant. And infusions are observed to act more strongly than decoctions of plants, the more subtile and volatile salts and spirits, which might be lost or corrupted by the latter, being obtained in their natural fate by the former. It is also observed that the finest, purest, and most volatile part is chat which first ascends in distillation. And, indeed, it should seem the lightest and most active particles required least force to disengage them from the subject.

47. The falts, therefore, and more active spirits of the car are got by infusion in cold water : but the resinous part is not to be dissolved thereby (a). Hence the prejudice which some perhaps may entertain against Tar-water, as a medicine, the use whereot might infame the blood by it's sulphur and refin, appears to be not well grounded ; it being indeed impregnated with a fine acid fpi.rit, balsamic, cooling, diuretic, and possessed of many other virtues (b). Spirits are supposed to consist of sales and phlegm, probably too fome:what of a fine oily nature, differing from oil in that it mixeth with water, and agreeing with oil, in that it runneth in rivulets by distillation. Thus much is allowed, that the water, earth, and fixed falt are the same in ail plants ; that, therefore, which differencech a plant or makes it whac ic is, the native spark or form, in the language of the chemists or schools, is none of thote things, nor yet the finest oil, which seemeth only it's receptacle or vehicle. It is observed by chemists, that all forts of balsamic wood afford an acid fpirit, - which is the volatile oily falc of the vegetable : Herein are chiefly contained their medicinal virtues, and by the trials I have made it appears, that the

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acid spirit in Tar-water poffefseth the virtues, in an eminent degree, of that of guaiacum, and to her medicinal woods.

48. Qualities in a degree too strong for human nature to subdue, and assimilate to itself, must hurt the constitution. All acids, therefore, may not be useful or innocent. But this seenreth an acid so thoroughly concocted, so gentle, bland, and temperate, and withal a fpirit so fine and volatile, as readily to enter the smallest vessels, and be assimilated with the utmost ease.

49. If any one were minded to diffolve some of the resin, together with the sale or spirit, he need only mix fome spirit of wine with the water. But such an intire solution of resins and gums, as to qualify them for entering and pervading the animal system, like the fine acid spirit that first flies off from the subject, is perhaps impossible to obtain. It is an apophthegm of the chemists, deriv. ed from Helmont, that whoever can make myrrh foluble by the human body, has the secret of prolonging his days : and Boerhaave owns that there seems to be truth in this, from it's resisting putrefaction. Now this quality is as remarkable in car, with which the ancients embalmed and preserved dead bodies. And though Boerhaave himself, and wher chemists before him, have given methods for making solutions of myrrh, yet it is by means of alcohol which extracts only the inflammable parts. And it doth not seem that any solucion of myrrh is impregnated with it's salt or acid spirit. It may not, therefore, seem ftrange if this water should be found more beneficial for procuring health and long life, than any solution of myrrh whatsoever.

50. Certainly' divers refins and gums may have virtues, and yet not be able for their grossness to

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