354 PEAT. 



This inference is indeed drawn from geological facts, 

 or from a comparison of the nature and antiquity of 

 these substances, implying more or less of exposure 

 to water. We cannot demonstrate this by experiment, 

 for want of the necessary element, time ; yet there 

 are chemical facts and analogies to support it. As 

 the chief difference between the bitumens arid the ana- 

 logous compounds, consists in the superior proportion 

 of oxygen in the latter, the process of bituminization 

 is, in some measure at least, one of deoxydation: while 

 the actual power of water to effect this, is proved by 

 the fact, that peat contains less oxygen than recent 

 vegetable matter. Thus also does the conversion of 

 turpentine into resin by exposure to air, imply deoxy- 

 dation ; though, with other analogous changes, always 

 attributed to the reverse. And the same effects, from 

 the same causes, are produced on the different liquid 

 bitumens and on the analogous compounds from vege- 

 table distillation ; though, in all these cases, new ba- 

 lances of the hydrogen and carbon are also formed. 

 There is also a further analogous case in the produc- 

 tion of adipocire ; demonstrating the power of water 

 to produce changes as great as that in question, and 

 sufficiently similar. 



But as it is my duty to examine falsehood as well as 

 truth, I must here note the hypothesis of some imagi- 

 nary chemists, that bitumen is produced from vege- 

 table matter by heat, and that coal therefore is a result 

 of fusion ; since a true theory of coal is here the ulti- 

 mate object. The adduced experiments are sufficiently 

 discreditable ; as the produce of the treatment of wood 

 in close vessels, so far from being coal, is not even bi- 

 tuminous : while only great carelessness could have 

 produced that bistre which was mistaken for asphal- 

 tum. Yet in the lignites or coals of the trap rocks. 



