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Show 78S SCOTCH FIR. SCOTCH FIR. to set fire to the latter, and there would be a great risk of losing the whole: as an additional safeguard, there is generally a vaulted canal, four orfive feet long, affixed to the mouths of the fur. nace, and terminated by a thick mud wall five or six feet in height. When every thing has been thus prepared, a moderate fire is kept up with very dry wood, and the juite boiledfive or six hours, the operators frequentlystirring it about with a large wooden ladle to prevent the impurities which sink to the bottom of the copper from taking fire,—a circumstance likely to occur, it is said, without such a precaution. ‘To ascertain whether the resinous matter is sufliciently boiled, a small quantity of it is taken out of the copper, and poured on a piece of wood; if, when it becomes cold, it may be reduced to powder by being pressed between the fingers, they knowthat the process is come plete, and then conduct it out of the copper into a large trough similar to what is used for receiving the raw juice fromthe pits, and placed in like manner on supports. It is necessary to filter the decoction, which is done by pouring it hot on some long straw neatly stretched over wooden bars which form a kind of horizontal grating; the thickness of the strawfilter is generally four orfive inches. The impurities and dregs remain onthe filter, and the juice runs through it pure into the trough. Before the juice becomes cold andfixed, it is let througha hole in the bottom of the trough into barrels, whereit is suffered to harden ; in this state it assumes a brown colourand brittle texture, and is called brai-sec, or rase. To convert it into yel- low resin: instead of tunning the hot juice at once into barrels, an eighth part of fresh water is mixed with it in the trough. The wateris acted upon so briskly by the hot decoction, that the whole continues to boil an hour or two, and the resin, froma brown colour, becomes at length of a fine yellow. It is afterwards deposited in barrels, and suffered to hardenlike the Craisec, The yellow resin, as ordered by the London college, is the result of a different Operation, but the properties of both these substances are so extremely alike, that they may be spoken of under the same head: we shall therefore reserve our account of them until we have described the mode of preparing the Essentian O1t. The process for obtaininng this oil, as directed in the Londo 789 Pharmacopceia, consists in distilling five pounds of the resinous juice with four pints of water, in a copper alembic. If one pound of the oil be redistilled with four pints of water, the result is called rectified oil of turpentine (oleum terebinthine rectificatum of the London and Edinburgh colleges). ‘The process of rectification is not unattended with danger ; for, unless the luting be very close, some of the vapouris apt to escape; and if the latter should takefire, the vessels will unavoidably burst. In some dispensatories this rectified oil is denominated ethereal, It does not differ very considerably in spécific gravity, smell, taste, or medical qualities, from the common essentia l oil. The oleumterebinthine, as we have before remarked, seems to be by far the most active part of the liquid resin of the pine, and is, on that account, much more frequently employed in me. dicine than any other preparation. Its exhibition, however, requires considerable caution, and the admonitions of Boerhaave, Lange, &c., on this subject, cannot betoostrictly attended to, The former of these authors, though its panegyrist, speaks of its violently affecting the head, producing bloody urine, and dangerously irritating the whole habit, whengiven injudicio usly orin too large doses; and the observation of practitio ners in general tends to confirmthis assertion. Hence, it is proper to employ a very few drops at first, and not to augment the dose without great circumspection. Thebest vehicle of this powerful medicineis honey, which, with the admixture of a due propor. tion of powdered liquorice root, forms-a good electuary . Iis use in diseases of the kidneys originating from ulcerations and obstructions in those organs, is unquestionable; whichis perhaps more than can be said of its alleged virtues in other com- plaints, and of those there are many for which medical writers of different ages have extolled the advantages of exhibiting tur. pentine, Chey he recommends it as a perfect cure for sciatica ; but, if I may be allowedto offer the result of my own profes. sional experience, its effects are in fewinstances successful for the removal of that tormenting disease; and even those cases which I have seen cured under the use of oil of turpentine, appeared to be rather of the symptomatic than of the idiopathi c Kind. Tt ig reasonable to presume that the sciatic nerve, from iS origin and course, may owe some ofits morbid affections to } . a1 obstruct ° . ed ureter, as well as to a rheumatic diathesis. In atching the state of the urinary excretion after the exhibition |