298 



formation of strata, such as we see in all the sedimentary rocks, and a 

 remarkable analogy may be observed between them. In the Old Red 

 Sandstone, in the carboniferous system for instance, the group is com- 

 posed of beds of hard, red, gritty rock, two or four feet thick, alternat- 

 ing with beds of soft, red, clayey shale, showing that in this, a sedi- 

 mentary group, hard, quartzose beds, and soft, argillaceous beds succeed 

 each other, like the hard basalt and the soft ochre beds of Antrim. 



The older rocks of the primary and transition systems present a 

 similar arrangement. Hard, gritty beds are found alternating with 

 soft, fine, slaty beds, each kind often varying in colour, as grey, green, 

 brown or red; and in thickness, from a few inches to 20, 50, or 100 

 feet, or more. 



The fusibility of igneous rocks generally exceeds that of other 

 rocks, for the alkaline, earthy, and ferruginous bases which they con- 

 tain make easily fusible salts, with the large quantity of silica, which 

 would be otherwise so refractory an ingredient. 



The layers of trap, as we see them at Garron Point, Fig. 4, and 

 many other good sections, are diversified : some are hard, some soft ; 

 they are mostly gray or blackish, with a few red. In aspect they are 

 unlike individually; yet, on the whole, they have a general resem- 

 blance, and any single layer would be known to belong to the family. 

 They are persistent, and often one layer can be seen in the face 

 of the cliff for a hundred feet, or from that to a thousand feet or 

 more, without much variation of thickness. At this locality the layers 

 are from two to six feet thick, and resemble the beds in a regular 

 quarry ; but this local regularity does not extend, by any means, over 

 large areas. 



As I shall have occasion to make frequent reference to the geography 

 of the north coast of Antrim, in the following observations I think it 

 desirable to give a statement in tabular form, showing the names of the 

 bays and headlands from the Bushfoot to Ballycastle, with the heights 

 of those headlands above sea level : — 



Names and Heights of the Principal Headlands on the North Coast of 

 Antrim, and of the Bays or Ports between them. — See PI. XXY. 



HEADLANDS AND BAYS. 



Feet high. 



1 . Bunk erry Point, west of Portcoon, . . . .119 



Portcoon Cave. 



2. Point, east of same, . . . . . .142 



Portnabaw. 



3. Weir's Snoot, opposite Great Stookaun, . . . 283 



Port Ganniv. 



4. Causeway, top of cliff, 307 



Port Noffer. 



5. Roveran Yalley Head, ..... . 327 



