LIGNITES. 315 



peat is proved by geological position, it is also inferred 

 from the bituminization of the vegetable matter : their 

 production too appearing to have long ceased, while 

 that of peat is matter of daily observation. Yet the 

 chemical nature of the former does not always corre- 

 spond accurately with their antiquity ; while the sub- 

 merged wood of peat occasionally presents marks of 

 bituminization, as just hinted. This difficulty, common 

 throughout mineralogy, among associated substances, 

 is an important fact in the history of these combus- 

 tibles, though it rnay be a blemish in a mere arrange- 

 ment. Still the main distinction must be sought in the 

 fact of bituminization ; of which peat at least, except 

 from the casual admixture of bitumen, presents no 

 traces. And though these lignites may retain the 

 marks of organization, so far, it is said, as to allow the 

 difference between the monocotyledonons and the dico- 

 tyledonous plants to be perceived, they are generally 

 flattened or compressed ; as the submerged woods 

 rarely are. 



If the boundary of the woody or organic lignites 

 towards peat is thus somewhat indefinite, so is it in- 

 definite towards coal. In a merely mineral point of 

 view, however, the most obvious distinction would seem 

 to consist in the mechanical rather than the chemical 

 nature of the specimens ; at least of those at the im- 

 mediate point of transition. In most cases, the woody 

 lignites retain some marks of the vegetable form, 

 though sometimes found in a pulverulent state: 

 whereas coal assumes the shape of a rock, even where 

 it still contains the remains of vegetables. But this 

 subject must be more strictly examined under the head 

 of Peat, where the chemical relations of the whole are 

 brought into comparison. It is sufficient that I have 



