3° 



that all the great coal fields of the world are belonging to the 

 Carboniferous Period, so called, indeed, from the occurrence of 

 such vast beds of carbonaceous matter. 



But as the Carboniferous System embraces a series of rocks 

 many thousand feet thick, and that as Coal occurs only in the 

 central division of the system, we must pierce through great thick- 

 nesses of rocks to get at the Coal in localities where the upper 

 portions of. the system is represented; and no Coal can be found 

 where the lower portion of the system forms the surface deposits. 

 The former conditions prevail in England and Scotland; the latter 

 unfortunately are too common in Ireland ; and hence, although we 

 have here the largest development of the Carboniferous System 

 perhaps in Europe, yet because we have chiefly the lower divisions 

 of it we have very little Coal. 



In this respect Ireland is not singular, indeed there are many 

 portions of the world much larger than Ireland that have no Coal 

 whatever or any representation of the Carboniferous System ; 

 further, there are portions of Europe equal to six times the super- 

 ficial area of Ireland that have not so great a variety of rocks as 

 occur in our single county of Antrim. 



Having explained the vegetable origin of all Coal, and the special 

 physical conditions favourable 'to its accumulation during the Car- 

 boniferous Period, Mr. Gray explained that the variety of Coal 

 from Anthracite to Lignite depended upon the nature of the flora 

 of which they were formed, and the- changes that have taken place 

 since their deposition. 



Every geological age was characterised by its own special flora, 

 of which the Coal of that age was formed. The Silurian Period 

 was characterised by flowerless plants, without proper stems or 

 leaves, such as Algae, or sea weeds. The Old Red Sandstone 

 Period produced flowerless plants with stems and leaves, as ferns, 

 &c, &c. The Carboniferous Period yielded flowering plants, as 

 palms and Liliacese, and all such as show parallel venation of 

 leaves. The Oolitic produced Coniferae and Cycadaceae, and the 

 Tertiary age produced the ordinary forest trees. 



Although differences in the vegetable matter constituting Coal 



