316 LIGNITES. 



here noted the transitions by which this production is 

 connected with coal. These remarks, however, apply 

 solely to those substances considered as minerals : the 

 geological distinctions are sufficiently marked, as it is 

 plain, that under the present arrangement many of 

 the lignites are, in a mineral view, coal. 



The varieties of the Coal lignites require no notice ; 

 and those of the woody ones enumerated by mineralo- 

 gists, are brown, or Bovey coal, surturbrand, jet, and 

 Cologne earth, or pulverulent lignite. Of these, how- 

 ever, the three first are not denned species, since they 

 rather tend to graduate into each other; as Bovey coal, 

 becoming darker and more bituminous, passes towards 

 surturbrand, and this becomes undistinguishable from 

 jet. If the others are not always powdery, they are at 

 least sufficiently tender to be easily reduced to that 

 state. To these I should add the casual specimens, of 

 no decided character, which occur among the various 

 strata; with the fragments of vegetables and fruits 

 generally described among the organic substances. The 

 origin and theory of the whole arc similar; but as they 

 are not of sufficient importance to require a separate 

 detail, they may be considered as casual fosssils in the 

 several strata where they occur. 



There are three obvious situations, sufficiently dis- 

 tinct, in which lignite occurs ; namely, in alluvial 

 soils, under stratified rocks, and connected with rocks 

 of the trap family. But the importance of some of 

 the deposits requires that the stratified rocks should 

 be distinguished by their more rigid geological con- 

 nexions. I shall here omit the coal which occurs in 

 the red marl, since it was already noticed in the last 

 chapter. It ought, indeed, in strictness, to rank here; 

 but being unimportant as a deposit, it is sufficient to 



