Chap. 4 !] Peat or ?urf. 267 



how far it is proper to confider peat among the fpe- 

 cies of coal j but as fome philofophers of great autho- 

 rity have attrib. --] every kind of coal to a vegetable 

 origin, and as fome kinds are decifively io, the reafon 

 of this arrangement will be obvious. What is properly 

 called peat is formed by the growth of a particular ve- 

 getable matter, peat mofs, which increafes to fuch a 

 degree in moorifh grounds as to form ftrata of many 

 feet in thicknef--. When peat is frefii dug from below 

 the furface, it is of a vifcid confidence, but hardens by 

 expofure to the air. It is often mixed with pyrites 

 and flony matters, which are feparated from it while 

 foft, in which ftate it is formed into oblong mafles for 

 fuel. When diftilled, it affords water, oil, and volatile 

 alkali, which are precifely the products afforded by 

 the diftillation of pit-coal. A kind of peat is found 

 near Newbury, in Berkfhire, which contains but little 

 earth, and confifts of wood, branches, twigs, roots, 

 with leaves, grafs, ftraw, and weeds. What is dug on 

 moors, under the name of turf, frequently contains a 

 mixture of peat. 



Coal, when heated and inflamed to fuch a degree 

 as to expel the more volatile parts, forms a kind of 

 mineral charcoal, called COKE, which is highly ufeful 

 in the property of affording a ftrong, clear, and lad- 

 ing fire, without forming a cohefive mafs, which would 

 prove very prejudicial in the fmelting of metals. It is 

 alfo ufed in drying thofe fubftances which would be 

 injured by the thick fmoke of common coal. 



Lord Dundonald was the firil perfon who improved 

 this proccfs, by collecting the tar and volatile alkali, 

 which are driven off from the coal, while it is con^ 

 verted into coke. Bis method has been adopted with 

 much advantage in feveral parts of Britain. The 

 coal is put into ovens, \vhich are heated by fires lighted 



beneath, 



