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earth near Woburn in Bedfordfhire, and alfo inthe fandy defarts to the weft of Egypt .

It not unfrequently happens that agatized■wood before the petrcfying procefs has "begun,has been corroded by worms, in which cafe notonly the perforation is filled with filiceousmatter, but even the fubftance of the wormitfelf has been compleatly agatized. -

Agatized wood difcovers flight traces of itsorigin by affording a few drops of a waterycmpyreumatic liquor by diftillation: it confiftshowever for the moil part of filex.

The origin of petrefied wood is generallyattributed to the gradual infiltration of thepetrefying fubftance, but to this theory, howeveriimple and ingenious, there are many import-ant objeftions.

WOOD-STONE. See the preceding article.

WOOD-OPAL. See Opal.

WOOL. Lame, Fr. IVolle, G.

This fubftance, the material of fuch import-ant manufactures, pofleffes fome curious che-mical properties, none of which however aremuch illuftrated by the various operations per-formed on it in manufacture, almoft all (thatof dyeing excepted) being purely mechanicalprocefies.

Some of the fimple chemical properties ofwool have been examined by M. Achard, a andcompared with the correfponding properties ofthe hair of different animals. The copiousgeneration of oxalic acid by treatment of wool■with nitric acid, has been particularly defcribedand explained by M. Berthollet in his beautifulrefearches on animal matter ; and the great fol-vent power of the cauftic fixed alkalies, hasbeen happily applied to fome ufe by M. Chaptalas a faponaceous compound. 1 *

Wool in the ftate in which it is taken fromthe flieep is always mixed with a great deal ofdirt and foulnefs of different kinds, and in par-ticular is ftrongly imbued with a natural ftrong-fmelling greafe. Thefe impurities are got ridof by waffling, fulling, and combing, by whichthe wool is rendered remarkably white, loft,clean, light, and fpringy under the hand. Whenboiled in water for feveral hours in a commonveffel, wool is not in any way altered in weightor texture, nor docs the water acquire any fen-fible impregnation.

A little aftion is Ihewn between water andwool by boiling for an hour in a high heat,with a Papin’s digefter,' the water acquires afmell like that of raw wool, and the wool isfomewhat whitened, but its weight is not fen-* Mem. de l’Acad. de Berlin, for 178*.

fibly changed, nor its texture materially altered.In this refpetSt it differs fomewhat from hair,the texture of which is much foftened whilft itis wet, by boiling in a digefter, but when dryit becomes quite cril'p and brittle.

Sulphuric acid added cold to wool producesneither heat nor any vapour, but after a fewhours the acid blackens, and the wool lofes itstexture, becomes foft and gelatinous, and fi-nally diffolves, forming a black thick acid li-quor.

The action of the nitric acid on wool is un-doubtedly the molt curious. When cold, thisacid only difengages a large quantity of azoticgas, but when warmed, much nitrous gas isgiven out,and at leaft two new acids are formed,viz. the malic and the oxalic, the latter is ingreater abundance than even from fugar and ni-trous acid, or any other hydro-carbonous balls.A fmall feum of a peculiar oil always arifesduring the adtion of nitrous acid on thefeanimal fubftances. See the article Oxa-lic Acid .

Muriatic acid when boiled on wool fimplydiffolves it. The folution is dark brown, andis not changed by the addition of water.

The adhion of the oxymuriatic acid has notbeen further examined than to difeover that itdoes not whiten wool as it does cotton, but onthe contrary, turns it to a pretty deep yellow,which may occafionally furnifh an ufeful me-thod of diftinguifhing the fibre of wool fromthat of cotton in any kind of cloth where theymay be mixed.

No effedt is produced by boiling wool in theoils, fixed or effential, or in alcohol.

The carbonated alkalies have little adhion onwool, but the cauftic fixed alkalies when di-gefted with it fpeedily weaken its fibre, reduceit to a foft gelatinous pulp, and finally make aperfect folution. The alkali at the fame timelofes its alkaline properties as it does incommon foap. This faponaceous folution ofwool is made for experiment in a few minutesby boiling bits of wool or flannel in a caufticalkaline folution, and it has been recommendedby Chaptal to be employed inftead of commonfoap in cleanfing cotton and other goods inmanufadtures, as by this means a number ofrefufe' bits and clippings of wool and woollencloth which are now thrown away may be putto fome ufe. This foapy folution does notlather well when agitated with water, never-thelefs it a£ts very powerfully in cleaning cloth.It has a ftrong and fomewhat offenfive fmell,

k An. Chim, Tom. xxi. e Achard.