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114. After having said so much of the uses of tar, I must farther add, that being rubb’d on them it is an excellent preservative of the teeth and gums; that it sweetens the breath, and that it clears and strengthens the voice. And, as its effects are various and useful, so there is nothing to be feared from the operation of an alterative so mild and friendly to nature. It was a wise maxim of certain ancient philosophers, that diseases ought not to be irritated by medicines. But no medicine difturbs the animal economy lefs than this (a), which, if I may trust my own experience, never produces any disorder in a patient when rightly taken.

115. I knew indeed a person who took a large glass of tar-water just before breakfast, which gave him an invincible nausea and disguft, although he had before received the greatest benefit from it. But if the tar. water be taken and made in the manner prescribed at the beginning of this esfay, it will, if I mistake not, have enough of the salt to be useful, and little enough of the oil to be inoffensive. I mean my own manner of making it, and not the American ; that sometimes makes it too strong, and sometimes too weak; which tar-water, how. ever it might serve as there used, merely for a preparative against the fmall-pox, yet I question whether it may be fitly used in all those various cases wherein I have found car-water so successful. Perfons more delicate than ordinary may render it palatable, by mixing a drop of the chemical oil of nutmegs, or a spoonful of mountain wine in each glass. It may not be amiss to observe, that I have known some, whose nice stomachs could not bear it in the morning, take it at night going to bed without any inconvenience; and that with some it agrecs beft warm, with others cold. It may be (a). 133.

made

made stronger for brute beasts, as horses, in whose disorders I have found it very useful, I believe more fo than that bituminous substance call'd Barbadoes

re

tas.

116. In very dangerous and acute cases much may be taken and often ; as far as the stomach can bear. But in chronical cafes, about half a pint, night and morning, may suffice ; or in case so large a dose should prove disagreeable, 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 so great virtue in so many different disorders, and especially in that grand enemy, the fever, must needs be a benefit to mankind in general. There are nevertheless three forts of people to whom I would peculiarly recommend it : Sea.faring persons, ladies, and men of studious and sedentary lives.

. 117. To failors and all sea-faring perions, who are subject to scorbutic disorders and putrid fevers, especially in long southern voyages, I am persua. ded this tar-water would be very beneficial. And this may deserve particular notice in the prefent course of marine expeditions, when so many of our country-men have perished by such distempers, contracted at sea and in foreign climates. Which, it is probable, might have been prevented, by the copious use of tar-water.

118. This fame water will also 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 cable, victims of va pours and indigestion.

119. Studious persons also pent up in narrow boles, breathing bad air, and stooping over their (a) 103.

books,

books, are much to be pitied. As they are debara red the free use of air and exercise, 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 hindrancé to their learning, and a great advantage to their health. My own sedentary course of life had long since thrown me into an ill habit, attended with maa ny ailments, particularly a nervous cholic, which rendered my life a burthen, and the more fo, because my pains were exasperated by exercise. But since the use of tar-water, I find, though not a perfect recovery from my old and rooted illness, yec such a gradual return of health and ease, that I esteem my having taken this medicine the greatest of all temporal blessings, and am convinced that, under providence, I owe my life to it.

120. In the distilling of turpentine and other balsams by a gentle heat, it hath been observed, that there riseth first an acid spirit (n) that will mix with water; which spirit, except the fire be very gentle, is lost. This grateful acid fpirit that first comes over, is, as a learned chemist and physician informs us, highly refrigeratory, diuretic, sudorific, balsamic or preservative from putrefaction, excellent in nephritic cases, and for quenching thirst, all which virtues are contained in the cold infusion, which draws forth from tar only it's fine Power or quintessence, if I may so say, or the native vegetable spirit, together with a little volatile oil.

121. The distinguishing principle of all vegetables, that whereon their peculiar smell, taste, and specific properties depend, seems to be some

(n) 7.

extremely

extremely fine and fubtile spirit, whose immediate vehicle is an exceeding thin volatile oil, which is itself detained in a grosser and more viscid resin or balsam, lodged in proper cells in the bark and feeds, and most abounding in autumn or wint'er, after the crude juices have been thoroughly concocted, ripened, and impregnated with solar light. The spirit itfelf is by fome supposed to be an oil highly subtilized, so as to mix with water. But luch volatile oil is not the spirit, but only it's vehicle. Since aromatic oils, being long exposed to air, will lose their fpecific fmell and taste, which fly off with the spirit or vegetable falt, without any sensible diminution of the oil.

122. Those volatile falts, that are set free and raised by a gentle heat, may juftly be supposed essential (@), and to have pre-existed in the ve. getable; whereas the lixivial fixed salts obtained by the incineration of the subject, whose natural constituent parts have been altered or destroyed by the extreme force of fire, are by later chemists, upon very good grounds, fupposed not to have pre-existed therein ; all such falts appearing, from the experiments of signor Redi, not to preserve the virtues of the reipeative vegetable fubjects; and to be alike purgative and in an equal degree, whatsoever may be the shape of their points, whether sharp or obtufe. But although fixed or lixivious salts may not contain the original properties of the subject; yet volatile salts raised by a ilight heat from vegetables are allowed to preserve their native virtues: and such falts are readily imbiled by water.

123. The most volatile of the falts, and the most attenuated part of the oil, may be supposed

(a) 8,

· the

the first and readiest to impregnate a cold infufion (b). And this will aslift us to account for the virtues of tar-water. That volatile acid in vegetables, which resists putrefraction, and is their great preservative, is detained in a subtile oil mircible with water, which oil is itself imprisoned in the resin or grosser part of the tar, from which it is easily set free and obtained pure by cold water,

124. The mild native acids are observed more kindly to work upon, and more thoroughly to diffolve, metallic bodies, than the strongest acid spirits produced by a vehement fire; and it may be suspected, they have the same advantage as a medicine. And as no acid, by the observation of some of the best chemists, can be obtained from the substance of animals thoroughly assimilated, it should follow, that the acids received into a healthy body must be quite subdued and changed by the vital powers: but it is easier to subdue and assimilate (e) the gentler than the stronger acids.

125. I am very sensible, that on such subjects arguments fall short of evidence : and that mine fall short even of what they might have been, if I enjoyed better health, or those opportunities of a learned commerce, from which I am cut off in this remote corner. I shall nevertheless go on as I have begun, and proceed by reason, by conjecture, and by authority, to cast the best light I can on the obscure paths that lie in my way.

126. Sir Isaac Newton, Boerhaave, and Homberg are all agreed, that the acid is a fine subtile substance, pervading the whole terraqueous globe ; . which produceth divers kinds of bodies, as it is united to different subjects. This according to

(b) 1, 7. re) 48.
H 2

Homberg

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