32 



Coal is composed of extinct forms of ferns and reed-like plants 

 characteristic of the Carboniferous age; whereas Lignite is com- 

 posed of a flora more like our modern pines and hard-wooded 

 plants. 



Ordinary Lignite is dull, brown, and fibrous, little removed from 

 compressed peat; but the Lignite of Antrim is solid, compact, 

 and often glistening with the lustre of true Coal; indeed, the 

 Lignite of Antrim is as much superior to ordinary Lignite as the 

 latter is better than peat. 



Ordinary Lignite is usually found interstratified with clay beds, 

 or strata of sedimentary deposits ; whereas the Lignite of Antrim 

 is found embedded in masses of volcanic rocks, the basaltic rocks 

 which cover the greater portion of Antrim, and extend into the 

 adjoining counties of Derry, Down, Tyrone, and Armagh. 



This basaltic crust was not laid down as a sedimentary rock, 

 like the white limestone it covers, but was forced up from below, 

 as molten lava through great rents and fissures now known as 

 " whin dykes," and the molten matter flowed over the surface of 

 the white limestone, not in one tremendous outburst, but by 

 successive overflows, as is proved by the semi-stratified arrange- 

 ment of the trap rocks seen at the Giant's Causeway cliffs, or 

 wherever a section of the trap rocks is exposed. 



Between the several outbursts of molten matter there must have 

 been long periods of rest, during which the surface was exposed to 

 atmospheric denudation, and swamps and lakes were formed as at 

 present, in which the ochre beds and iron ores now found so ex- 

 tensively over the Trappean area were deposited; and rank forests 

 doubtless skirted the margin of the lakes, the remains of which 

 constitute the Lignite beds and carbonaceous layers occurring so 

 frequently between the basaltic rocks, not only in Antrim but in 

 Derry and Down ; in Derry they have been found at Ballynascreen, 

 Slieve Gallon, and Magilligan ; in Antrim they occur at the Giant's 

 Causeway, Rathlin Island, Port Bradden, Ballintoy, Glenarm, 

 Killymurris, Shane's Castle, Kilcorrig, Carnmoney, Ballypallidy, 

 Tardree; and in the County Down a bed of Lignite occurs at 

 Laurencetown. 



