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

39. It is remarked by Theophraftus, that all plants and trees while they put forth have most humour, but when they have ceased to germinate and bear, then the humour is ftrongest and most fheweth the nature of the plant, and that, therefore, trees yielding refin fhould be cut after germination. It seems alfo very reasonable to fuppofe the juice of old trees, whofe organs bring no new fap, fhould be better ripened than that of others.

46. The aromatic flavours of vegetables feem to depend upon the fun's light, as much as colours. As in the production of the later, the reflecting powers of the object, fo in that of the former, the attractive and organical powers of the plant co-operatate with the fun (a). And as from Sir Ifaac Newton's experiments it appears, that all colours are virtually in the white light of the fun, and fhew themfelves when the rays are feparated by the attracting and repelling powers of objects, even fo the specific qualities of the elaborate juices of plants, feem to be virtually or eminently contained in the folar light, and are actually exhibited upon the feparation 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 hath been obferved by fome curious ana-. tomists, that the fecretory veffels 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 origi nally imbued with it's own proper juice, attracts none but that fort; by which means fo many vari ous juices are fecreted in different parts of the body. And perhaps there may be fomething analogous to this, in the fine abforbent veffels of plants, which may co-operate towards producing that endless variety of juices, elaborated in plants from the fame earth and air.

42. The balfam or effential oil of vegetables contains a spirit, wherein confift the specific qualities, the smell and taste of the plant. Boerhaave holds the native prefiding fpirit to be neither oil, falt, earth, or water; but fomewhat too fine and fubtile to be caught alone and rendered vifible to the eye. This when fuffered to fly off, for instance, from the oil of rosemary, leaves it deftitute of all flavour. This fpark of life, this fpirit or foul, if we may fo fay, of the vegetable departs without any fenfible diminution of the oil or water wherein it was lodged.

43. It should seem that the forms, fouls, or principles of vegetable life, fubfift in the light or folar emanation (a), which in refpect of the macrocoẩm is what the animal fpirit is to the macrocofm; the interior tegument, the fubtile inftrument and vehicle of power. No wonder then that the ens primum or fcintilla fpirituofa, as it is called, of plants fhould be a thing fo fine and fugacicious as to escape our niceft fearch. It is evident that nature at the fun's approach vegetates; and

(a) 40.

languishes

languishes at his recefs; this terreftrial globe feeming only a matrix difpofed and prepared to receive life from his light; whence Homer in his hymns styleth earth the wife of heaven, ἄλοχ' ουρανᾶ ἀφερόεντος.

44. The luminous fpirit which is the form or life of a plant, from whence it's differences and properties flow, is fomewhat 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 feveral 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 fpirit; part of which fpirit exhales through the leaves and flowers, and part is arrefted by this unctuous humour that detains it in the plant. It is to be noted this effential oil animated, as one may fay, with the flavour of the plant is very different from any fpirit, that can be procured from the fame plant by fermentation.

45. Light impregnates air (a), air impregnates vapour; and this becomes a watery juice by diftillation having rifen firft in the cold ftill with a kindly gentle heat. This fragrant vegetable water is poffeffed of the fpecific odour and tafte of the plant. It is remarked that diftilled oils added to water for counterfeiting the vegetable water can never equal it, artificial chemiftry falling short of

the natural.

46. The lefs violence is ufed to nature the better its produce. The juice of olives or grapes iffuing by the lighteft preffure is beft. Refins that drop from the branches fpontaneously, or ooze upon the flighteft incifion, are the finest and most

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fragrant. And infufions are obferved to act more ftrongly than decoctions of plants, the more fubtile and volatile falts and fpirits, which might be: loft or corrupted by the latter, being obtained in their natural state by the former. It is alfo obferved that the finest, pureft, and moft volatile part is that which firft afcends in deftillation. And, indeed, it should feem the lightest and most active. particles required leaft force to difengage them from the fubject.

47. The falts, therefore, and more active spirits of the tar are got by infufion in cold water: but the refinous part is not to be diffolved thereby, (a). Hence the prejudice which fome perhaps may entertain against Tar-water, as a medicine, the ufe whereof might inflame the blood by it's fulphur and refin, appears to be not well grounded; it being indeed impregnated with a fine acid fpirit, balfamic, cooling, diuretic, and poffeffed of many other virtues (b). Spirits are fuppofed to confift of falts and phlegm, probably too fomewhat 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 deftillation. Thus much is allowed, that the water, earth, and fixed falt are the fame in all plants; that, therefore, which differenceth a plant or makes it what it is, the native spark or form, in the language of the.. chemifts or schools, is none of thofe things, nor yet the finest oil, which feemeth only it's receptacle or vehicle. It is obferved by chemifts, that. all forts of balfamic wood afford an acid fpirit, which is the volatile oily falt of the vegetable : Herein are chiefly contained their medicinal virtues, and by the trials I have made it appears, that the

(a) Sect. 7. (b) Sect. 42, 44.

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acid fpirit in tar-water, poffeffeth the virtues, in an eminent degree, of that of guaiacum, and other medicinal woods.

48. Qualities in a degree too ftrong for human nature to fubdue, and affimilate to it felf, must hurt the conftitution. All acids, therefore, may not be useful or innocent. But this feemeth an acid fo thoroughly concocted, fo gentle, bland, and temperate, and withal a fpirit fo fine and volatile, as readily to enter the smallest veffels, and be affi milated with the utmost ease.

49. If any one were minded to diffolve fome of the refin, together with the falt or fpirit, he need only mix fome fpirit of wine with the water. But fuch an intire folution of refins and gums, as to qualify them for entering and pervading the animal fyftem, like the fine acid spirit that first flies off from the fubject, is perhaps impoffible to obtain. It is an apopthegm of the chemifts, derived from Helmont, that whoever can make myrrh foluble by the human body, has the fecret of prolonging his days: and Boerhaave owns that there feems to be truth in this, from it's refifting putrefaction, Now this quality is as remarkable in tar, with which the ancients embalmed and preserved dead bodies. And though Boerhaave himself, and other chemifts before him, have given methods for making folutions of myrrh, yet it is by means of alcohol which extracts only the inflammable parts. And it doth not feem that any folution of myrrh is impregnated with it's falt or acid fpirit. It may not, therefore, feem ftrange if this water fhould 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 grofinefs to

pafs

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