330 LIGNITES. 



tire fusion and ultimate change of the original strata 

 into crystalline trap ; so that, here also, the lignites 

 have equally escaped. 



Even however if lignite should be found sur- 

 rounded by a crystalline trap, it does not follow that 

 the rock has not been in a state of fusion, or at least 

 of softness, sufficient to enable its parts to assume a 

 crystalline character. The siliceous schists beneath 

 basalt often assume that concretionary structure which 

 proves a softened condition of the same nature ; and, 

 in such cases, shells are often found entangled in the 

 mass, sometimes deformed by pressure, as the lignites 

 themselves are, yet retaining their integrity, with'much 

 of their original characters. Neither is the bitumi- 

 nous matter of the strata dissipated in such cases ; 

 since, the associated limestones and shales are often 

 highly bituminous. Charcoal also, I need not say, is 

 indestructible by heat, when protected from air ; and 

 though sometimes altered in chemical character by 

 the loss of its hydrogen, it still retains its form. 

 Hence then, even the woody lignites might remain 

 surrounded by fluid trap till it had cooled, as coal 

 also unquestionably does, where the ordinary coal 

 strata are found in similar circumstances. If this par- 

 ticular case has not occurred in trap, it is known to 

 have happened with lava, so that the difficulty is com- 

 pletely removed. In Italy, trees have been found en- 

 tangled in perfect lavas, having burnt out where 

 there was access of air; and in the isle of Bourbon, 

 the trunks of palms have thus also been observed 

 wrapped in lava; the stony matter having further pene- 

 trated the fissures so as to have assumed their shapes. 



Hence then might the lignites of trap often preserve 

 their vegetable organic character, together with their 

 chemical nature, in considerable perfection ; while, in 

 other cases, they might be entirely converted into 



