LIGNITES. 325 



questionable cases, the wood is flattened, as if from great 

 pressure ; possessing also those peculiar chemical pro- 

 perties by which the lignites are distinguished from 

 peat. In such situations also they vary in quality; con- 

 taining more or less bitumen intermixed with the pe- 

 culiar compound which constitutes peat ; while those 

 which are most deeply situated are commonly also the 

 most highly bituminized. The case of Bovey offers 

 examples of this nature, if it be really one of alluvial 

 lignite ; since the different strata are separated by the 

 loose matter which fills this valley, and the more per- 

 fect lignites occupy the lowest positions. 



The depth of the superincumbent strata, and the 

 number of alternation;} in these cases, present consi- 

 derable variety ; but the recorded observations do not 

 yet admit of any general conclusions deserving of much 

 regard. The total depth at Bovey, is said to be seventy 

 feet; this space including all the lignites together with 

 the alternating beds of clay. In Iceland, the lignite 

 appears to be generally much more superficial, and is 

 found in the form of boards ; as if produced from the 

 trunks of trees flattened by pressure. This is the va- 

 riety to which the name of Surturbrand has been par- 

 ticularly applied. That of Bardestrand is found on a 

 hill of moderate elevation, beneath strata of sand and 

 clay alternating with peat ; and here, as at Bovey, the 

 upper beds are imperfect, the middle intermediate in 

 quality, and the lowest most complete. At Arnafiord, 

 it is accompanied by shale, containing bones, with 

 fragments of branches and roots. I need only add, that 

 the position of jet is sometimes analogous. 



It thus appears that the lignites buried under allu- 

 vial soils, occur in the several forms of brown coal, or 

 common woody lignite,, pulverulent lignite, or Cologne 

 earth, snrturbrand, and jet. To whatever different cii> 



