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Show 792 SCOTCH FIR. of procuring tar which Duhamel states to have been practisedin the Valais, and which seems to be the best that has been adopted, It is usual to cut downthe pines intended to be burnt for the extraction of tar, in the course of the summer. The operators, knowing the quantity that will be wanted, regulate the extent of the hewing andtearing upof ‘the trees, so as that the materials maybe neither too green nor too dryat the time of preparing their ovens, for to make good tar they should not be more than half dry. As all parts of the pine (the trunk, branches, and eventhe bark) yield this substance, the branches are cut of a length proportionate to thesize of the oven, and the thicker parts chopped into little billets similar to what are usedin fag. gots. The ovens are shapedlike an egg placed on its smaller end, and are composed of earth and stone, the floor being formed of one or more pieces of freestone, which are very nicely joined and hollowedlike the inside of an egg-shell. Onone sidethere is a hole about an inch and a half in diameter, and six inches in depth ; to the external orifice of this, andfive or six inches higher thanthe bottom of the oven, a gun-barrel of alarge caliber is affixed, and there is a large iron grate placed at the bottom of the oven. The dimensions of the oven vary according to the quantity of wood intended to be burnt, the largest being about ten feet high, five orsix feet in diameter in the middle, and two feet and a half at the mouth or superior part. The walls are about a foot and a half in thickness. To about two-thirds of the height these are constructed with freestone, but abovethat with oven-earth. When the ovens are finished, and quite dry and tight, bundles or faggots of the wood, tied up with hazel or vine rind, are set upright on the grating; the ligatureis cut by means of a blade fixed at the end of a stick ; and the pieces are spread about, the interstices being filled with chips. This first layer being properly made, a second faggot is let down, then a third, and so on until the ovenis full, as high as the hand can reach, when chips andshavings are laid on to the thickness of three or four inches, and the mouth is covered up withflat stones piled one upon another so as to closeall gaps exceptat the centre, where an opening is left four or five inchesin dia meter. All things being thus prepared, the chips at the top are set on fire; and the operators, who from experience are enabled to ascertain when the materials are sufficiently kindled, seize the proper time to shut up the mouth entirely with a flat stone; and SCOTCH FIR. they stop up with earth eyeryinterstice from which smoke is seen to escape. The wood then becomes reduced to charcoal, and the resinous part of it, mixed with the sap, flows through the grate down into the cavity at the bottomof the oven. When this cavity is full up to the place where the iron tubeis fixed, the tar flows into barrels placed to receiveit. It is from custom alone that the persons whosuperintend the Operation ascertain when the wood has given out all its resinous liquor; theythen open the top of the oven, removing the stones, and collecting the soot which lodges intheir interstices as well as on the sides of the oven, and which forms a kind of lamp-black; lastly, they take out the charcoal that has lodged on thegr ating, and recommence the operation by laying on woodas before. Such impurities as are heavier than the tar, with which they were mixed, remain on the stone that serves as a floor to the oven, whilst the tar itself flows onthe surface through the tube, which, as we have remarked before, is five or six inches above the level of the stone. As far as we can judge, all the art of the operation consists in a proper management of the fire, for if the oven be too closely stopped, the fire is extinguished, the woodis but imperfectly charred, and very little tar is extracted; but if, on the contrary, the wood burn too briskly, a great proportion of the resinous matter is consumed, When the fire is properly re. gulated, there is no flame inthe oven; the heat and smoke, which are reverberated on the wood, cause the resin and sap to flow from the latter together. It would seem that a morecer tain mode of regulating the heat would be, instead of closing the top of the oven with stones and turf, to adapt register s of different sizes to a kind of dome, which might form the upper part of Mf, and renderthe structure more neat and commod ious. Tarhas been used as a medicine both externa lly and internally, The antients had a high opinion of its efficacyin pulmon ary dis. €ases, supposing it to promote expectoration, relieve dyspnea, and check spitting of blood. Diosco rides particularly speaks of its utility in these cases. He also recomm ends it to be applied to ulcers, which, he says, it fills up and heals, whether they be situated on the surface of the body, or in the ears, throat, or other interna] parts. In fact, there is no end to the praises be. stowed by medical writers on the propert ies of tar, which, if Ve are to give credit to all the accounts given of it, is equal to the cure ofall the maladies of the human frame. The colleges |