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ope seem se trees. The an

for, or picea of the Latins, to be the male for of Theophrastus. This was probably the spruce fir ; for the picea, according to Pliny, yields much relin, loves a cold and mountainous situation, and is diftinguished, tonsili facilitate, by it's fitness to be fhorn, which agrees with the spruce fir, whereof I have seen close shorn hedges.

27. There seems to have been some confusion in the naming of these trees, as well among the ancients as the moderns. The ancient Greek and Latin names are by later authors applied very differently. Pliny himself acknowledgeth, it is not easy even for the skilful to distinguish the trees by their leaves, and know their sexes and kinds: and that difficulty is since much encreased, by the discovery of many new species of that evergreen tribe, growing in various parts of the globe. But defcriptions are not so easily misapplied as names. Theophrastus tells us, that witus differeth from W Oxn, among other things, in that it is neither so tall nor so streight, nor hath so large a leaf. The fir he distinguisheth into male and female: the latter is softer timber than the male, it is also a taller and fairer tree, and this is probably the silver fir.

28. To say no more on this obscure business which I leave to the critics, I shall observe that according to Theophrastus not only the turpentine trees, the pines, and the firs yield resin or tar, but also the cedars and palm trees; and the words pix and resina are taken by Pliny in so large a sense as to include the weepings of the lentiscus and cypress, and the balms of Arabia and Judæa; all which perhaps are near of kin, and in their most useful qualities concur with common tar, especially, the Norvegian, which is the most liquid and best for medicinal uses of any that I have experienced. Those trees that grow on mountains, exposed to

the

the fun or the north wind, are reckoned by Theo. phrastus to produce the best and purest tar: And the Idæan pines were distinguished from those growing on the plain, as yielding a thinner, sweeter, and better scented tar, all which differences I think I have observed, between the tar that comes from Norway, and that which comes from low and swampy countries.

29. Agreeably to the old observation of the Peripatetics, that heat gathereth homogeneous things and disperseth such as are heterogeneous, we find chemistry is fitted for the analysis of bodies. But the chemistry of nature is much more perfect than that of human art, inasmuch as it joineth to the power of heat that of the most exquisite mechanism. Those who have examined the structure of trees and plants by microscopes, have discovered an admirable variety of fine capillary tubes and vessels, fitted for several purposes, as the imbibing or attracting of proper nourishment, the distributing thereof through all parts of the vegetable, the discharge of fuperfluities, the secretion of particular juices. They are found to have ducts answering to the tracheæ in animals, for the conveying of air; they have others answering to lacteals, arteries, and veins. They feed, digest, respire, perfpire and generate their kind, and are provided with organs nicely fitted for all those uses.

30. The sap vessels are observed to be fine tubes running up through the trunk from the root. Secretory vessels are found in the bark, buds, leaves, and flowers. Exhaling vessels for carrying off excrementitious parts, are discovered throughout the whole surface of the vegetable. And (though this point be not so well agreed) doctor Grew in his Anatomy of plants, thinks thereappears circulation of the fap, moving downwards in the root, and feeding the trunk upwards.

31. Some difference indeed there is between learned men, concerning the proper use of certain parts of vegetables. But whether the discoverers have rightly guessed at all their uses or no, thus much is certain, that there are innumerable fine and curious parts in a vegetable body, and a wonderful similitude or analogy between the mechanism of plants and animals. And perhaps some will think it not unreasonable to suppose the mechanism of plants more curious than even that of animals, if we consider not only the several juices secreted by different parts of the same plant, but also, the endless variety of juices drawn and forined out of the same foil, by various species of vegetables ; which must therefore differ in an endless variety, as to the texture of their absorbent vessels and fecretory ducts.

32. A body, therefore, either animal or vegetable, may be considered as an organised system of tubes and vessels, containing several sorts of fluids. And as fluids are moved through the vessels of animal bodies, by the systole and diastole of the heart, the alternate expansion and condensation of the air, and the oscillations in the membranes and tunicks of the vessels; even so by means of air ex: panded and contracted in the tracheæ or vessels made up of elastic fibres, the fap is propelled through the arterial tubes of a plant, and the ve. getable juices, as they are rarefied by heat or condensed by cold, will either ascend and evaporate into air, or descend in the form of a gross liquor.

33. Juices therefore, first purified by straining through the fine pores of the root, are afterwards exalted by the action of the air and the vessels of the plant, but, above all, by the action of the sun's

ir; or descend in ihher ascend and at or con

light; which at the fame time that it heats, doch wonderfully rarefy and raise the faps till it per. spires and forms an atmosphere, like the effluvia of animal hodies. And though the leaves are fuppof. ed to perform principally the office of lungs, breathing out excrementitious vapours, and drawing in alimentary; yet it seems probable, that the reciprocal actions of repulfion and attraction are performed all over the surface of vegetables, as well as animals. In which reciprocation, Hippocrates supposeth the manner of nature's acting, for the nourishment and health of animal bodies, chiefly to.consist. And, indeed, what share of a plant's nourishment is drawn through the leaves and bark, from thar ambient heterogeneous fluid called air, is not easy to say. It seems very considerable and altogether necessary, as well to vegetable as animal life. .

34. It is an opinion received by many, that the fap circulates in plants as the blood in animals:. that it ascends through capillary arteries in the trunk, into which are inosculated other vessels of the bark answering to veins, wbich bring back to the root the remainder of the fap, over and above what had been deposited, during it's ascent by the arterial vessels, and secreted for the several uses of the vegetable throughout all it's parts, ftem, branches, leaves, Aowers, and fruit. Others deny this circulation, and affirm that the sap doth not return through the bark vessels. It is nevertheless agreed by all, that there are ascending and defcending juices; while some will have the ascent and defcent to be a circulation of the same juices through different vessels: others will have the ascending juice to be one fort attracted by the root, and the descending another imbibed by the leaves, or extremities of the branches : lastly, others think that

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the same juice, as it is rarefied or condensed by heat or cold, rises and subsides in the same tube. I shall not take upon me to decide this controversy. Only I cannot help observing, that the vulgar argument from analogy between plants and animals Joseth much of it's force, if it be considered, that the supposed circulacing of the fap, from the root or lacteals through the arteries, and thence returning, by inosculations, through the veins or bark vessels to the root or lacteals again, is in no sort conformable or analogous to the circulation of the blood.

35. It is sufficient to observe, what all must acknowledge, that a plant or tree is a very nice and complicated machine (a); by the several parts and motions whereof, the crude juices admitted through the absorbent vessels, whether of the root, trunk, or branches, are variously mixed, separated, altered, digested, and exalted in a very wonderful manner. The juice as it passeth in and out, up and down, through tubes of different textures, shapes, and sizes, and is affected by the alternate compression and expansion of elastic vefsels, by the vicissitudes of seasons, the changes of weather, and the various action of the solar light, grows still more and more elaborate,

36. There is therefore 'no chemistry like that of nature, which addech to the force of fire, the most delicate, various, and artificial percolation (b). The incessant action of the fun upon the elements of air, earth, and water, and on all sorts of mixed - bodies, animal, vegetable and fossil, is supposed to perform all sorts of chemical operations. Whence it should follow, that the air contains all sorts of chemic productions, the vapours, fumes, oils, falts,

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