LIGNITES. 331 



coal. In the lignites of Meissner, the woody kinds 

 are actually changed into coal when they are in con- 

 tact with basalt. I may now barely say, that the de- 

 gree of pressure may have been sometimes such as to 

 prevent the entire dissipation of the volatile matters, 

 and that the degree of heat and of pressure, having 

 been inferior to those required for the fusion of the 

 lignite into shapeless coal, the vegetable structure has 

 been preserved, as it would have been in charcoal 

 under similar circumstances; while the form has per- 

 haps also been preserved through the protection af- 

 forded by unfused fragments or earthy matters entan- 

 gled together with it in the trap. 



I have only to add on this subject, that as long as a 

 sect existed to maintain that all trap rocks had been 

 formed under the sea, every lignite thus connected 

 with them was supposed to have been entangled in 

 the same place. The problem was sufficiently diffi- 

 cult ; yet not conspicuous among the other difficul- 

 ties consequent on this hypothesis. But as I have 

 shown that these rocks have been produced under the 

 same variety of circumstances which attend volcanoes 

 it is easy to understand how they should have entan- 

 gled fragments or deposits of wood imbedded in ter- 

 restrial alluvia, just as modern volcanoes have done. 

 And it is further plain, that, as in the case of Meissner, 

 the irruption of trap into strata already containing 

 lignites might have produced similar appearances ; the 

 clays or marls undergoing the changes which com- 

 monly result from this cause, while the vegetable or 

 coaly substances would thus become involved in the 

 trap itself, or in the rocks which it had modified. 



These enquiries respecting the much misappre- 

 hended nature of the basaltic lignites having involved 

 the theory of that division, it only remains to enquire 

 into that of the older and the alluvial ones ; and while 



