WOOD. 



ferved in this cafe to be moft fatal. The exhalation of 

 the fap from the wood of the veflel is certainly the occafion 

 of this, and if it could be contrived to have this fap pro- 

 perly exhaled before the timber was ufed, it would not only 

 prevent this mortality among the men, but the veffel itfelf 

 would be the founder and the better for it. Deflandes, 

 Trait, de Phyf. 



Woods are diftinguifhed into divers kinds, with regard to 

 their natures, properties, virtues, and ufes. Of wood, con- 

 fidered according to its quahties, whether ufeful, curious, 

 medicinal, &c. the principal is that called timber, ufed in 

 building houfes, laying floors, roofs, machines, &c. See 

 Timber. 



Woods valued on account of their curiofity are, cedar, 

 ebony, mahogany, walnut-tree, box, calambo, &c. which, by 

 reafon of their extraordinary hardnefs, agreeable fmell, or 

 beautiful polifh or grain, are made into cabinets, tables, 

 combs, beads, &c. 



The medicinal moods are, guaiac, which the Spaniards call 

 iigno/anSo; aloes, or agallochum ; fqffafras, nephriticum, fan- 

 ial, logwood, afpalathum, eagle-wood, or pan d'aquilo, &c. 



Woods ufed in dyeing are, the Indian wood, Brajil, Cam- 

 peche, &c. 



In extracting the colouring-matter of dye-woods, and in 

 making fome other colours for the ufe of calico-printers, Mr. 

 Parkes obferves (Chem. Eff. vol. ii.), that it is of great 

 confequence to heat the veffels by fleam ; forby this method 

 of preparing decoctions, the workmen are prevented from 

 ever giving the materials a greater heat than that of 212°; 

 and the injury which was formerly done by the burning of 

 the grofler matters at the bottom and fides of the copper is 

 avoided. Several manufafturers, fays this ingenious chemift, 

 have now adopted this method. This leads us to take notice 

 of a beneficial application of charcoal, as a flow conduftor 

 of caloric, for preferving an equable temperature. Ground 

 charcoal, it is faid, will conduft heat more flowly than even 

 dry fand, in the proportion, according to Guyton, of three 

 to two. Accordingly, all thofe veflels which are heated by 

 fteam, if they were made double, and the fpace between the 

 inner and outer veffel filled with ground charcoal, the heat 

 would be fo prevented from efcaping, that any given tempe- 

 rature might be maintained for a long time, and thus there 

 would be a material faving in the article of fuel. Moreover, 

 when churches or other large buildings are to be warmed 

 by fteam, thofe parts of the condufting-pipes which are not 

 within the buildings fliould be always furrounded in this 

 manner, and then no heat could efcape until it had been con- 

 veyed to the fpace which it was intended to warm by it. 

 Thus alfo in the manufaftories of ftarch, paper, gun- 

 powder, blue, and a variety of other articles, every part 

 of the apparatus for drying thefe by (team, and which is 

 not aftually within the drying-rooms, ought to be fecured 

 m the fame way. The common fteam-working apparatus, 

 and other culinary utenfils, would be much improved by 

 being fitted with double covers, and by filling up the inter- 

 mediate fpaces with carbonaceous matter. Moreover, by 

 fecuring the condufting-pipes in this manner, buildings 

 might be effeflually warmed, and procefles condufted at any 

 diftance from the boiler, as fteam is the moft faithful carrier 

 of heat that can poflibly be ; for it cannot depofit it on any 

 bodies that have already acquired the temperature of 212°. 

 It is alfo this non-conduAingr property of charcoal that ren- 

 ders it fo common, fays Fourcroy, cited by Parkes, in 

 France as a material for coating furnaces, and for confin- 

 ing the heat, to which ufe its incombuftible nature adapts 

 it in a peculiar manner, as it is the moft refradcry body that 

 8 



is known, provided it be excluded from oxygen. Charcoal 

 is applicable to other purpofes in domeftic economy ; fuch 

 as the preferving of animal food from taint, by covering it 

 with a few pieces of frefh -burnt charcoal, and the recovery 

 of it by boiling it for fome minutes in water with a few 

 ounces of fuch charcoal. By the fame m-ans, molafles or 

 treacle may be deprived of its difagreeable tafte, fo that it 

 might be ufed inftead of fugar. A patent has likewife been 

 taken out for refining fugar by means of charcoal by M. 

 Cronftat, who required for it, of the joint body of fugar- 

 bakers in London, a remuneration of 50,000/.; and Mr. 

 Parkes apprehends, that in a fmall concern of ihis kind efta- 

 bliftied in the metropohs, which manufaftures double loaves 

 of a finer quality than thofe of any other houfe, the purpofe 

 is efFefted by the fame means. The empyreumatic flavour 

 acquired by fome brandies in diftillation may be removed, 

 fays the ingenious writer now cited, by digefting them in 

 charcoal ; and common malt-vinegar, boiled on charcoal, be- 

 comes colourlefs, without lofing its ftrength. Water, which 

 in long voyages acquires a difagreeable tafte and fmell from 

 long ftanding in the wooden caflts, may be purified by filtra- 

 tion through ground charcoal ; or it may be kept fweet in 

 cafl<s that have been charred withinfide. 



For the above-mentioned purpofes, the charcoal fhould be 

 frefh made, or heated red-hot under a cover of fand, imme- 

 diately before it is ufed ; and the requifite quantity (hould 

 be previoufly afcertained by experiment. In fome cafes, i: 

 fhould be ufed in the form of powder, having been pounded 

 immediately from the fire, before it has been expofed to the 

 air, and the refidue fhould be prcferved for future ufe in 

 bottles clofely flopped. For other ufe3 to which charcoal is 

 applied, fee Charcoal and Carbon. 



Wood ufed for fuel is required of various kinds, in re- 

 gard to the various works to be performed by it. 



Neri every where commends oak for tlie wood to be 

 burnt in the glafs-houfes, as the propereft wood for making 

 a ftrong and durable fire with a good flame. 



Imperato, on the contrary, commends afh on the fame 

 occafion ; becaufe, as he fays, it gives a fubftantial rather 

 than a great flame : and Camerarius defervedly commends 

 juniper wood, as affording a lafting, ftrong, and fweet fire, 

 could plenty of it be had. Among the ancients, Pliny 

 commends light dry wood ; and Plutarch, the tamarifk in 

 particular, for making the glafs-houfe fires ; but glafs- 

 making requires fo great a fire, as cannot be eafily made 

 from fuch wood. Nor can afh be proper, becaufe, though 

 it gives a good fire, it foon decays. Merret's Notes on 

 Neri, p. 275. 



If wood be burnt in the open air, the greateft part of it 

 will be diffipated in gas. Common oak, properly charred, 

 will lofe only from fds to -r'uths of its weight ; whereas, 

 if the fame kind of wood be burnt in an open fire- 

 place, the refiduum of the combuftion will not be more 

 than about ^g^th, or ^^-th of the original weight of the 

 wood employed. Dr. Watfon fays, that he obtained 22 

 grains of charcoal from 96 of dry oak : others have given 

 different refults. From Neumann (Chem. vol. ii.) we learn, 

 that for the reduftionof themetalhc oxyds, the charcoal of the 

 heavier woods, e. g. that of the oak and beech, is preferable ; 

 and that, for common fuel, fuch charcoal gives the greateft 

 heat, and requires the moft plentiful fupply of air to keep 

 it burning, while thofe of the lighter woods preferve a 

 glowing heat vrith a much lefs draught of air ; and that 

 for purpofes which require a Heady and ftill fire, charcoal 

 made from wood previoufly divefted of its bark fhould be 

 employed, as it is the cortical part which crackles and flies 



off 



