314 



CHAP. XLIIL 



Lignites. 



IN conformity to an accepted arrangement, which I do 

 not approve, yet do not at present choose to depart 

 from, the present chapter includes every combustible 

 deposit following the magnesian limestone. It com- 

 prises many which are nndtstingnishable from the 

 former coal, both in general disposition and in mineral 

 character, together with the several substances which 

 are lignites in the mineral sense of that term : the 

 latter forming an important object in the theory of coal, 

 as being the link by which it is connected with peat. 



The gradation of geological relations from the "in- 

 dependent" coal to the most superficial woody lignite 

 in the upper alluvia, and thence to peat, is sufficiently 

 perfect ; while from that through the old red sandstone, 

 we can pursue this gradation into the primary strata. 

 But the mineralogical or chemical gradation is even 

 more complete : and, in this respect, the woody lig- 

 nites hold a station more nicely intermediate between 

 coal and peat ; some of them approaching as nearly to 

 the submerged wood of peat in chemical characters as 

 in their appearance ; while, in both these respects, there 

 are varieties at the other extremity of the series, scarcely 

 differing from coal, and finally identical with it. I must 

 however remark, that while almost every ligneous sub- 

 stance found beneath alluvial soil, and bearing marks 

 of bituminization, is here ranked as a lignite, I have 

 found it more expedient to class with peat the sub- 

 merged wood of the most recent alluvia, even though 

 it should be slightly bituminized ; on account of its 

 different connexions with that substance. 



While the superior antiquity of the woody lignite to 



