300 



books, from museums, or even from mountains, and to adopt one so 

 simple as will be barely sufficient to show such physical differences as 

 are easily perceptible to the eye, either in hardness, grain, or colour, in 

 traversing the country. 



Fig. 5. 



Curved Balsaltic Columns, about 50 feet high, resting on Chalk, at White Head, 

 near Carrickfergus. 



In taking a glance over the basaltic country of Berry and Antrim, 

 it might be thought that the trap, or basalt, is all composed of one 

 great eruption of melted matter, poured out at once over the white 

 limestone, or chalk, as it then existed ; but this notion does not stand 

 the test of reasoning. In well-exposed sections, it is seen all in level 

 layers, and it is much more in accordance with what we see in nature, 

 to suppose that each layer was a distinct eruption, for it generally 

 makes a distinct variety of rock. Neither does it appear that any one 

 kind was poured out at one time over the whole area. At Aughna- 

 hough (Fig. 1, p. 275) soft blackish wacke (b, b, b,) rests on the white 

 limestone, and therefore appears to have been the first rock spread out 

 in that place. At Cave Hill, it is nearly similar. At Whitehead, near 

 Carrickfergus, the chalk is covered by hard, columnar trap (Pig. 5), 

 exhibiting some of the most magnificent curving columns in the 

 country, 50 feet in height, with soft, level layers covering them at 

 top. At Fair Head, it is greenstone, and rests both on chalk and on 

 coal-measures, at Murlogh Bay, PI. XXYI. At Bengore Head, tabular 

 trap (PI. XXIV.) is the lowest rock visible ; but there may be other 

 varieties, for the underlying rock is below the sea level. In fact, there 

 is no regular succession of the basaltic layers, either high up in the 

 mass or low down immediately on the chalk. 



