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

39. It is remarked by Theophrastus, 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 strongest and most Thewech the nature of the plant, and that, therefore, trees yielding resin should be cut after germination. It seems also very reasonable to suppose the juice of old trees, whose organs bring no new lap, should be better ripened than that of others.

40. The aromatic favours 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-operatate with the sun (a). And as from Sir Isaac Newton's experiments it appears, that all colours are virtually in the white light of the fun, and shew themfelves when the rays are separated by thë attracting and repelling powers of objects, even so the specific qualities of the elaborate juices of plants, seem to be virtually or eminently contained in the solar light, and are actually exhibited upon the feparation of the rays, by the peculiar powers of the capillary organs in vegetables, artracting and imbibing certain rays, which produce certain Aavours and qualities, in like manner as certain rays, being reflected, produce certain colours, fal 36, 37.

ards products of plant,ogous to

41. It hath been observed by fome curious ana-. tomists, 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 origi nally 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 essential 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 instance, from the oil of rosemary, leaves it deftitute 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, fouls, or principles of vegetable life, subsist in the light or solar emanation (a), which in respect of the macrocosm is what the animal spirit is to the macro. cosm; the interior tegument, the subtile inftru. ment and vehicle of power. No wonder then that the ens primum or scintilla spirituosa, as it is cal. led, of plants should be a thing so fine and fugacicious as to escape our nicest search. It is evident that nature at the sun's approach vegetates; and

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Janguishes at his recess; this terrestrial globe seeming only a matrix disposed and prepared to receive life from his light; whence Homer in his hymns styleth earth the wife of heaven, arox cupavő á secevtos.

44. The luminous spirit which is the form or life of a plant, from whence it's differences and properties flow, is somewhat extremely volatile, It is not the oil, but a thing more subtile, 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 seeds, 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 spirit exhales through the leaves and Aowers, and part is arrested by this unctuous humour that detains it in the plant. It is to be noted this efiential oil animated, as one may say, with the fa.. vour of the plant is very different from any spirit, that can be procured from the same plant by fermentation,

45. Light impregnates air (a), air impregnates. vapour; and this becomes a watery juice by diftilJation having risen first in the cold still with a kindly gentle heat. This fragrant vegetable water is possessed 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 its produce. The juice of olives or grapes iffuing by the lightest pressure is best. Relins that drop from the branches spontaneously, or ooze upon the lightest incision, are the finest and most

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fragrant. And infusions are observed to act more: strongly than decoctions of plants, the more sub-. tīle and volatile salts and spirits, which might be: loft or corrupted by the latter, being obtained in their natural state by the former. It is also observed that the finest, purest, and most volatile part is that which first ascends in deftillation. 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 tar 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 whereof mighe inflame the blood by it's sulphur and resin, appears to be noc well grounded ; it being indeed impregnated with a fine acid fpirit, balsamic, cooling, diuretic, and possessed of many other virtues (6). Spirits are supposed to consist of sales and phlegm, probably too somewhat of a fine oily nature, differing from oil in that it mixech with water, and agreeing with oil, in that it runneth in rivulets by destillation. . Thus much is allowed, that the water, earth, and fixed salt 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 chemists or schools, is none of those things, nor yet the finest oil, which seemeth only it's recepacle or vehicle. - It is observed by chemists, that. ull sorts of balsamic wood afford an acid fpirit, which is the volatile oily falt of the vegetable :: Herein are chiefly contained their medicinal virtues, ind by the trials I have made it appears, that the

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

48. Qualities in a degree too strong for human nature to subdue, and assimilate to it self, must hurt the conftitution. All acids, therefore, may not be useful or innocent. But this seemeth an acid so thoroughly concocted, so gentle, bland, and temperate, and withal a spirit 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 refin, together with the sale or spirit, he need only mix some spirit of wine with the water, But such an intire soluţion 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 apopthegm of the chemists, derived from Helmont, that whoever can make myrrh foluble by the human body, has the secret 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 car, with which the ancients embalmed and preserved dead bodies. And though Boerhaave himself, and other cheniifts 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 doch not seem that any folution of myrrh is impregnated with it's falt or acid fpirit. It may not, therefore, feem strange 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 groftness to

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