in the Dist illation of Wood, &c. 271 



hard compact substance resembling bituminous shale in its smell 

 and consistence. 



Reverting to the cliemical nature of the other Hgnites, there 

 is very httle reason to doubt that those among them vvliich ap- 

 proach the nearest to a state of perfect bituminization, would 

 have given results nearly similar, but I could not pursue the ia- 

 vestigation for want of sufficient specimens. From peat we should 

 expect but a mixed matter, varying between the bitumen of 

 wood and true bitumen, according to the degree of change pre- 

 viously undergone; for that the process of bituminization is the 

 effect of water, and not of fire, is rendered probable, as much 

 by these trials as by the geological observations above mentioned. 

 The conversion of bituminized wood into true coal may possibly 

 be the effect of a consolidation produced by the agency of fire ; 

 but 1 shall leave this argument in the hands of those who have 

 undertaken the defence of this theory — having entered into this 

 train of reasoning, not by design, but from the imavoidable con- 

 catenation of experiments *. 



A circumstance occurred in the coaly residuum of the wood 

 tar which it is worth while to notice, although of an accidental 

 nature, and not essentialTy affecting the history of the vegetable 

 liitumen or pitch which I have described. It bore no resem- 

 blance to common charcoal, but was more like black lead. It 

 \vas as glossy, and although not so soft, marked paper with a 

 similar streak. It was inflated, and therefore minutely scaly, 

 and porous, and was attracted by the magnet. Muriatic acid 

 took up a portion of iron from it, as it does from many varieties 

 of plumbago, and the remainder resembled plumbago alter it had 

 been submitted to the action of acids. 



It was also exceedingly difficult to burn, requiring a long con- 



• That I may not interrupt the text, I will add, in a note, a cursory ac- 

 count of the black matter vvliicli is deposited in boi^s, and which seems to 

 be the substance giving the pitchy appearance to the more com] act va- 

 rieties of peat. I have not seen it in the soft state in which it is fiiac pro- 

 cured. 



When dry, it is black, sometimes dull, sometimes witli the lustre of 

 asphaltum. It is heavier than water. It is not electric. It is brittle, and 

 breaks with a fracture intermediate between the splintery and conchoidul, 

 resembling asphaltum generally in its external characters. Exposed to a 

 red heat it is incinerated, giving a smoke possessing a modified smell of 

 vegetable (pyroligneous) acid. It is not acted upon by boiling alcohol, 

 ether, or naphtha; and in this latter circumstance its diflfereiice from 

 asphaltum is marked. Neither is it soluble in boiling water. It is 

 readily dissolved in lixivium of potash, and by nitrous acid. It appears 

 to be formed of the vegetable elements in the state of transition to bitu- 

 ni«n, the carbon having been first held in solution, as it 's in tlie water of 

 dunghills, by the other matters with which it was combined, and being at 

 length consolidated by the dissipation of a portion of them The produce 

 wf itb combustion shows it is combined with both hydrogen and oxygen. 



It 



