PEAT. 353 



attributed to fire what has been the effect of water. 

 This is the only agent capable of producing that 

 change: and these papyri are, simply, peat, passing 

 towards lignite. 



The relative nature of the bituminous and the cor- 

 responding compounds, like that of the change from 

 peat to lignite, can be inferred by the same species of 

 examination. In both cases, carbon and hydrogen 

 form the bulk ; but the carbon seems to bear a greater 

 proportion in the former, as they also produce more 

 ammonia and less acid ; indicating differences which I 

 need not explain to chemists, as I need not here pur- 

 sue the chemical enquiry. Yet I must note, that I 

 here use the term lignite, only for the organic or truly 

 mineralogical ones: the geological lignites being, 

 chemically, as well as mineralogically, coal. 



Having already shown that peat is a compound 

 slightly removed from simple vegetable matter, and 

 intermediate between that and lignite, I have thus also 

 further cleared the way for the geological question 

 which concerns these. But the change to lignite is 

 gradual ; producing varieties in which the two com- 

 pounds that form the essence of peat, and bitumen, are 

 mixed in different proportions. The same action of 

 water also, which converts the vegetable into peat, 

 can produce the further change to bitumen, as it does 

 in the earth ; though the time required is very consi- 

 derable, since that occurs only under a very high anti- 

 quity in this substance. And as the most perfect lig- 

 nites are also the most antient, the degree of bitumi- 

 nization in any more modern one being also gradually 

 less, down to the confines of peat, so do I infer that 

 the prolonged action of water has effected the ulti- 

 mate change, as it has produced all the inferior ones, or 

 can change and has changed peat into perfect lignite^ 



VOL. II. A A 



