320 



by the great heat of the incandescent greenstone in contact with it. 

 The fossils, however, retain their forms, and can be recognised in the 

 altered hard rock. 



Fig. 10. 



Section showing the protrusion of Greenstone into beds of Lias at 

 Skerries, near Portrush. 



1 + . 



a, the crystalline greenstone which underlies it. 



b, represents the lias with its clays, shales, and limestones, which occur in 

 the bay east of Portrush. 



By this explanation it can be understood how the fossils found in 

 the altered lias were considered to be found in trap. Thousands of am- 

 monites may be seen in this black flinty rock immediately east of the 

 greenstone protrusion of Portrush, where a thin layer of altered lias 

 clay reposes on it at high-water mark. Besides the fossils, those 

 Skerries protrusions show how a horizontal dyke, or one nearly so, 

 may be thrown out from a melted mass of greenstone into other strata. 



Lignite, or Wood Coal. 



In Dobourdieu's Statistical Survey of the County of Antrim he 

 gives, at page 87, a letter from Rev. Robert Trail, on wood coal. This 

 subject is one that should not be passed over in the geology of Antrim ; 

 and as my own experience in matters of detail of this kind is not ex- 

 tensive, I shall quote Mr. Trail's letter, which appears to me to be all 

 an inquiring mind could desire. He lived upon the spot, he quarried 

 the coal, and burned it, and he was able to describe the details regard- 

 ing it. He says— " In most places where I have observed this sub- 

 stance, columns of basalt are placed over it. In my own quarry on 

 the glebe it is to be found underneath twenty feet of solid rock in a 

 compressed state, or flattened appearance; the outward edges, however, 

 have preserved, in many instances, a degree of roundness, and I have 



