WOOD. 



off in fparks during combuftion, wliich the coal of the wood 

 itfelf feldom does. The charcoal of wood is faid to be eflential 

 to the perfeftion of bar-iron ; but when wood became fcarce, 

 and government re(lri£led its ufe, cinders and coke were 

 fubftituted for it ; and thus the quality of Englifli iron was 

 fo much debafed, that Ruffian and Swedifli iron, which is 

 prepared by means of the coal of wood, are employed by 

 thofe who work in this metal. The fuperioiity of the iron 

 made with charcoal is attributed by M. Haflenfratz to its 

 combination with potafiiiim. It was by i Eliz. c. 15. that 

 it was enafted, that no oak, beech, or afh-timber, one foot 

 fquare at the ftub, (hould be converted into charcoal for 

 making iron in any part of England or Wales, except in 

 the county of Suffex, the weald of Kent, and certain parifhes 

 in the county of Surrey. This reftriftion led to the prac- 

 tice of making bar-iron with the coke of pit-coal, the 

 method of preparing which was kept a fecret from the 

 generality of the trade. When Mr. Henry Home pub- 

 fiihed his " Eflays on Iron and Steel," in the year 1773, 

 he gave direftions for a better method than they had before 

 known of charring pit-coal, fo as to make it a proper fuc- 

 cedaneum for wood-charcoal in the maiiufafture of iron. 

 Since that time the coke of pit-coal has come into very general 

 ufe, fo that the confumption of this fubftaiice is now very 

 conilderable. (See Coke.) Crayons of charcoal are bell 

 made of the willow ; whereas the coals of the hard woods, 

 fuch as box and guaiacum, are much harder than otliers, 

 whilfl the charcoal of the kernels of fruits is quite foft and 

 friable. As a pigment, the coal of ivory, or that which is 

 procured by burning real ivory in clofed veflels, is the moft. 

 intenfely black, and the moft beautiful. Tlie bell charcoal 

 for ufe as a powder for cleaning the teeth is made from the 

 fhell of the cocoa-nut. The difference between the char- 

 coals of animal and vegetable fubftances may be determined 

 by the following tett. A vegetable coal will burn on a 

 red-hot iron into white afhes, which will be readily diflblved 

 by fulphuric acid into a bitterifh liquor ; whilll the afhes 

 of animal fubftances are Httle affefted by that acid, and 

 form with it a compound with a very diff^erent tafte. ( See 

 Ashes, Carbon, Charcoal, and CvfiPoivder.) For 

 the method of charring wood, fee Timber and Char- 

 ring of Pojis. This appears to have been a very ancient 

 praftice. The piles that formed the foundations of the 

 Temple of Diana at Ephefus, not long fince taken up, ap- 

 peared to have been charred ; and about fifty years ago 

 iome oak-ftakes were found in the bed of the Thames in the 

 very fpot where Tacitus fays that the Britons fixed a num- 

 ber of fuch ftakcs, to prevent the paflage of Cxfar's army ; 

 and thefe ftakes, which were charred to a coiifiderable depth, 

 had completely retained their form, and were firm at the 

 heart. About fixty years ago one of the timbers that fup- 

 ported Trajan's bridge over the Danube, near Belgrade, 

 was taken up, and the outer part, to the depth of half an 

 inch, was found to be converted into an agate, the inner 

 parts being (lightly petrified, and the central being ftill 

 perfeft wood, though this tin:ber had been in the water 

 1700 years. (See Kirwan's Geological Eflays, cited by 

 Parkes in hisEffa^s, vol. ii.) Many other inftances occur 

 of wood petrified and converted, more or lefs, into agates of 

 various colours. Writers on this fubjeft have recommended 

 the pradlice of charring every piece of wood before it is 

 placed in the ground. Dr. Watfon, (hte biftiop of Lan- 

 daff', ) in his " Chemical EfTays," vol. iii. fnggefts the 

 propriety of charring all the wood that is ufed in mines and 

 iubterraneous drains, and particularly that which covers 

 troughs, through which a current of water pafles, and 

 which rot in a few years by the alternate change of wet and 



7'r>i, conneaion we may add, on the authority 



of Chaptal, in his " Chcmiftry applied to the Arts," that 

 when old chefnut and other trees are rotted within the trunk, 

 and threatened with fpeedy deftrudion by the progrefs of 

 the carious trunk, it may be flopped by applying fire to 

 the decayed part, fo as to char the whole of the neighbour- 

 ing furfaces. 



Wood, in Gardening, is a term ufed to fignify the (hoots 

 or branches left in fruit-trees. See Pruning, &c. 



Wood, an epithet applied to various forts of weeds. 

 See Weed. 



Wood and Bart of Trees, Canker or Erofion of, in Agri- 

 culture and Garde/ling, a difeafed ftate in thefe parts of them. 

 It has been ftated by a late philofophical writer, that the 

 caufe feems to be an excefs of alkaline and earthy matter in 

 the defcending fap, as he often found carbonate of lime on 

 the edges of the canker in apple-trees ; and that ulmin, 

 which contains fixed alkali, is abundant in the canker of the 

 elm. The old age of a tree, in this refpeft, is, it is thought, 

 faintly analogous to the old age of animals, in which the 

 fecretions of folid bony matter are always in excefs, and 

 the tendency to offification great. 



It is fuggefted, that perhaps the apphcation of a weak 

 acid to the difeafed part might be of ufe ; or that where 

 the tree is of great value, it might be watered occafionally. 

 See Canker. 



Wood, Lignln? in Chemiflry, the fub ft ance which con- 

 ftitutes the bafis of wood ufually fo called. 



To obtain this fubftance in a ftate of purity, it is necef- 

 fary to digeft wood in a fufficient quantity of water and 

 afterwards of alcohol, by which means all foreign fubftances 

 fjluble in thefe fluids will be removed ; the fimple -woody 

 fibre will thus remain, which poflefles the following pro- 

 perties. 



It is compofed, in general, of longitudinal fibres eafily 

 feparable from one another. Thefe fibres, when very much 

 fubdivided, become fomewhat tranfparent. They have no 

 fmell nor tafte, and are not altered by expofure to the 

 atmofphere. 



The woody fibre is infoluble in water and alcohol. It is 

 foluble in a weak alkaline folution without being decom- 

 pofed, and may be again feparated by an acid. Concen- 

 trated alkaline folutions render it brown, and decompofe it, 

 efpecially when affifted by heat. 



When heated it becomes black without melting, exhales 

 ftrong acrid fumes, and leaves a charcoal, retaining exaftly 

 the form of the original mafs. When diftilled in clofe 

 veflels it yields an acid liquor, of a peculiar tafte and fmell, 

 called the pyroligneous acid, a[id which was properly confi- 

 dered as a diftinCt acid. Fourcroy and Vauquelin, however, 

 long ago demonftrated, that it confifts of nothing but the 

 acetic acid combined with an empyreumatic oil. (See Ace- 

 Tou.s and Pyroligneous Acid. ) Pure acetic acid is now 

 prepared from wood both in this country and France. 



The fibre of different woods has been analyfed by Gay 

 Liiflac and Thenard by means of the oxymuriate of potafh. 

 The followinnf are the refults : 



100.00 



lOO.OO 



Wood wlitii burnt with a fraothered flame leaves, as is 



well 



