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made ftronger for brute beafts, as horfes, in whofe diforders I have found it very ufeful, I believe more fo than that bituminous fubftance call'd Barbadoes tar.

116. In very dangerous and acute cafes much may be taken and often; as far as the ftomach can bear. But in chronical cafes, about half a pint, night and morning, may fuffice; or in cafe fo large a dose should prove difagreeable, half the quantity may be taken at four times, to wit, in the morning, at night going to bed, and about two hours after dinner and breakfast. A medicine of fo great virtue in fo many different diforders, and especially in that grand enemy, the fever, muft needs be a benefit to mankind in general. There are nevertheless three forts of people to whom I would peculiarly recommend it: Sea-faring perfons, ladies, and men of studious and fedentary lives.

117. To failors and all fea-faring perfons, who are fubject to fcorbutic diforders and putrid fevers, efpecially in long fouthern voyages, I am perfuaded this tar-water would be very beneficial. And this may deferve particular notice in the present courfe of marine expeditions, when fo many of our country-men have perifhed by fuch diftempers, contracted at fea and in foreign climates. Which, it is probable, might have been prevented, by the copious use of tar-water.

118. This fame water will alfo give charitable relief to the ladies (a), who often want it more than the parish poor; being many of them never able to make a good meal, and fitting pale, puny, and forbidden like ghosts, at their own table, victims of vapours and indigeftion.

119. Studious perfons alfo, pent up in narrow holes, breathing bad air, and ftooping over their

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books, are much to be pitied. As they are debarred the free use of air and exercife, this I will venture to recommend as the best fuccedaneum to both. Though it were to be wished, that modern scholars would, like the ancients, meditate and converse more in walks and gardens and open air, which, upon the whole, would perhaps be no hindrance to their learning, and a great advantage to their health. My own fedentary courfe of life had long fince thrown me into an ill habit, attended with many ailments, particularly a nervous colic, which rendered my life a burden, and the more fo, because my pains were exafperated by exercife. But fince the ufe of Tar-water, I find, though not a perfect recovery from my old and rooted illness, yet fuch a gradual return of health and ease, that I efteem my having taken this medicine the greatest of all temporal bleffings, and am convinced that, under Providence, I owe my life to it.

120. In the diftilling of turpentine and other balfams by a gentle heat, it hath been obferved, that there rifeth firft an acid fpirit (n), that will mix with water; which fpirit, except the fire be very gentle, is loft. This grateful acid fpirit that first comes over, is, as a learned chemift and phyfician informs us, highly refrigeratory, diuretic, fudorific, balfamic or prefervative from putrefaction, excellent in nephritic cafes, and for quenching thirst, all which virtues are contained in the cold infufion, which draws forth from tar only its fine flower or quinteffence, if I may fo fay, or the native vegetable fpirit, together with a little volatile oil.

121. The diftinguishing principle of all vegetables, that whereon their peculiar fmell, tatte, and specific properties depend, feems to be fome (n) 7. extremely

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extremely fine and fubtile fpirit, whofe immediate vehicle is an exceeding thin volatile oil, which is itfelf detained in a groffer and more vifcid refin or balfam, lodged in proper cells in the bark and feeds, and moft abounding in autumn or winter, after the crude juices have been thoroughly concocted, ripened, and impregnated with folar light. The fpirit itself is by fome fuppofed to be an oil highly fubtilized, fo as to mix with water. But fuch volatile oil is not the fpirit, but only its vehicle. Since aromatic oils, being long expofed to air, will lose their specific fmell and taste, which fly off with the fpirit or vegetable falt, without any fenfible diminution of the oil.

122. Those volatile falts, that are fet free and raised by a gentle heat, may juftly be fuppofed effential (a), and to have pre-exifted in the vegetable; whereas the lixivial fixed falts obtained by the incineration of the fubject, whofe natural conftituent parts have been altered or destroyed by the extreme force of fire, are by later chemifts, upon very good grounds, fuppofed not to have pre-existed therein; all fuch falts appearing, from the experiments of fignor Redi, not to preferve the virtues of the refpective vegetable fubjects; and to be alike purgative and in an equal degree, whatfoever may be the fhape of their points, whether sharp or obtufe. But although fixed or lixivious falts may not contain the original propefties of the fubject; yet volatile falts raised by a flight heat from vegetables are allowed to preferve their native virtues: and fuch falts are readily imbibed by water.

123. The moft volatile of the falts, and the moft attenuated part of the oil, may be fuppofed (a) 8.

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the firft and readieft to impregnate a cold infufion (b). And this will affift us to account for the virtues of tar-water. That volatile acid in vegetables, which refifts putrefaction, and is their great prefervative, is detained in a fubtile oil mifcible with water, which oil is itself imprifoned in the refin or groffer part of the tar, from which it is eafily fet free and obtained pure by cold wa

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124. The mild native acids are observed more kindly to work upon, and more thoroughly to diffolve, metallic bodies, than the strongest acid fpirits produced by a vehement fire; and it may be fufpected, they have the fame advantage as a medicine. And as no acid, by the obfervation of fome of the beft chemifts, can be obtained from the fubftance of animals thoroughly affimilated, it should follow, that the acids received into a healthy body muft be quite fubdued and changed by the vital powers: but it is easier to fubdue and affimilate (c) the gentler than the ftronger acids.

125. I am very fenfible, that on such subjects arguments fall fhort of evidence: and that mine fall fhort even of what they might have been, if I enjoyed better health, or thofe opportunities of a learned commerce, from which I am cut off in this remote corner. I fhall nevertheless go on as I have begun, and proceed by reafon, by conjecture, and by authority, to caft the beft light I can on the obfcure paths that lie in my way.

126. Sir Ifaac Newton, Boerhaave, and Homberg are all agreed, that the acid is a fine fubtile fubftance, pervading the whole terraqueous globe; which produceth divers kinds of bodies, as it is united to different fubjects. This, according to (c) 48.

(b) 127.

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Homberg, is the pure falt, falt the principle, in it felf fimilar and uniform, but never found alone. And although this principle be called the falt of the earth, yet it fhould feem it may more properly be called the falt of the air, fince earth turned up and lying fallow receives it from the air. And it fhould feem that this is the great principle of vegetation, derived into the earth from all forts of manures, as well as from the air. This acid is allowed to be the cause of fermentation in all fermented liquors. Why therefore, may it not be fuppofed to ferment the earth, and to conftitute that fine penetrating principle, which introduces and affimilates the food of plants, and is fo fugitive as to escape all the filtrations and perquifitions of the moft nice obfervers?

127. It is the doctrine of Sir Ifaac Newton and Monfieur Homberg, that, as the watry acid is that which renders falt foluble in water, so it is that fame which joined to the earthy part makes it a falt. Let it therefore be confidered, that the organs (d) of plants are tubes, the filling, unfolding, and diftending whereof by liquors, doth conftitute what is called the vegetation or growth of the plant. But earth itself is not foluble in water, fo as to form one vegetable fluid therewith. Therefore the particles of earth must be joined with a watry acid, that is, they must become falts in order to diffolve in water; that so, in the form of a vegetable juice, they may pafs through the ftrainers and tubes of the root into the body of the plant, fwelling and diftending its parts and organs, that is, increafing its bulk. Therefore the vegetable matter of the earth is in effect earth changed into falt. And to render earth (d) 30, 31, 35.

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