CAR

CAR

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is fpread a ftratum of brufh-wood, and fo on al-ternately till the pile has acquired the hcighthof about fix feet, forming a truncated pyramid,or truncated cone. The top and Tides are now-covered to the thicknefs of two inches more orlefs with dry earth, or the dull remaining froma former burning; and over all is laid neatly acovering of fods fo as to exclude the air, exceptfrom the lowed: ftratum of brulh-wood, andhere the fods are laid with as great intervalsbetween them as can be allowed confident-ly with giving a firm fupport to the upperl'ods'which reft upon them. The pile beingthus arranged one of the workmen mounts tothe top of it, and withdraws the flake that wasdriven into the centre of the area, filling up thefpace with dry chips, and laying a lighted ftickon the top. The fire foon begins to fpreaddownwards, and torrents of fmoke pour forthfrom the interlaces between the lower fods andfrom the chimney in the centre: after fometime a light column of flame rifes out of thechimney which is immediately flifled by the ap-plication of a piece of turf laid lightly on, fo asalmoft but not entirely to clofe the vent. In anhour or two the fire will have made confider-able progrefs, and occafional explofions will takeplace, from the copious difengagement and hid-den combuftion of carburetted hydrogen, onwhich occafions all the vigilance of the work-men is required. The approach of an explofionis indicated by a rumbling kind of noife withinthe pile which terminates in a loud burft as ifthe whole mafs was torn in pieces; no materialderangement however happens except that afmall part of the covering is thrown out of itsplace, the extent of the damage being indicatedby the flame and fmoke that burft forth. Thefeorifices as foon as they appear mull be carefullyclofed by a few fpadefuls of dry earth. Intwelve or fourteen hours the explofions willhave ceafed, and the fmoke will diminifh; theworkmen mull now begin gradually to clofe upthe interftices at the bottom of the pile, begin-ning on the windward fide, and then for thenext twenty hours no further attention will berequired except to fee that no accidents happen:the fire quietly fpreads towards the circum-ference, which when it has reached the fmoakalmoft entirely ceafes, and the whole mafs ap-pears glowing in every part. The wood is nowthoroughly charred, and nothing more is necef-fary than to extinguilh the fire: this is done bythrowing on a quantity of dried earth fufficientto cover the whole to the depth of a few inches,

* Mufhet in Phil.

and taking care to flop up all cracks as foon asthey appear. In the courfe of the fourth dayfrom building the pile, the charcoal is generallyfit to be removed, and this is afcertained bymaking an opening into the mafs while yetwarm, and if the fire is entirely extinguillied itis immediately taken to pieces, but if on ex-pofure to the air it begins to glow the openingis carefully covered, and the breaking up of thepile is deferred to the next day.

The above is the French method of preparing■charcoal; but the mode followed in Scotland with the moft fuccefs differs fo confiderablyfrom that juft defcribed, as to require particu-lar mention. The French charcoal is chieflycalculated for culinary ufes, and is thereforemade of confiderably fmaller wood than theScottifh, which is entirely employed in the ironworks. b The procefs begins by raifing a plotof ground a little higher than the furroundingfurface, and bringing it to a {lightly convex form.In the centre of this area is placed a circle ofHicks, the loofe ends of which are directed in-wards fo as to crofs each other a few inchesbelow the top, and thus form a kind of cup ofthe fhape of an inverted cone. Round this in-terior circle are ranged fucceflive concentriccircles, formed by truncheons from one to teninches in diameter, care being taken that thetruncheons in any one circle are of the famediameter, and that one built of the largeftwood is always fucceeded by another of thefmalleft wood, in order that there may be asfew interfaces as poflible. The outermoft circleis compofed of brufh-wood. When the pilemeafures from twenty to thirty feet in diameterit is fufficiently large. A coating is now laidon of turf, the grafly fide next to the wood,and dry earth is heaped up around the bottomof the pile, and well rammed down in order toprevent the admiffion of air. The mafs is lightedin the centre, by dropping into the cup formedby the interior circle fome dry lighted chips,and in proportion as thefe are confumed otherfmall pieces are put in during the firft fouror five days. When the upper part of the pileis fufficiently kindled, a row of holes, eachabout two inches in diameter is opened a fewinches below. The hole at the top is thenclofed, and the fire now compleatly kindled{lowly defcends to the circle of air holes. Asfoon as it has reached this point, which is knownby a remarkable diminution of the fmoak andvapour ; a fecond row of holes is opened at thediftance of fix or eight inches below the firft

Mag. iii. j>. is.