184 Irish Volcanoes. 



diameter, and few of them less than 15 inches. The sepa- 

 rate parts or joints of the columns vary in length from a few 

 inches to as much as four feet. 



There is generally a bold sea off the north coast of Ireland, 

 and when the wind comes from a northerly quarter, especially 

 from north-west, it is not a pleasant place from whence to start 

 on a boating excursion. But as it is quite impossible to see 

 and do justice to the peculiar and grand scenery of the coast 

 two or three miles east of the Causeway without viewing it from 

 the sea, those who are bad sailors must either make up their 

 minds to considerable discomfort or wait for a very calm .day. 

 There is little danger, however, as the boats are built for the 

 work, and the boatmen very experienced. , It is an expedition 

 worthy of any trouble. Lofty and vertical cliffs with two 

 ranges of columnar basalt overlying, and separated by rough, 

 irregular, and gloomy masses of similar rock, appear in a suc- 

 cession of small bays, the cliff gradually rising, and the posi- 

 tion of the columnar part of the rock rising also till we reach 

 the part called the Pleskin. Here the columnar rocks attain 

 an elevation of nearly 400 feet, and are extremely bold, appear- 

 ing even to overhang. 



A peculiar feature of the cliffs near the Causeway is the 

 occurrence at frequent intervals of wide spaces in the rock, 

 filled with a variety of the common basaltic rock. These are 

 locally called whin-dykes, a name certainly given by some geo- 

 logical visitor, but now familiar in the neighbourhood. These 

 appear to be, and probably are, for the most part, mere clefts 

 and crevices caused by the contraction of the original lava-bed 

 while cooling, and afterwards filled up by other lava currents 

 of later date. They are sometimes softer and more easily acted 

 on by weather than the adjacent rock, and then they form 

 narrow inlets. Elsewhere they are harder and less affected 

 by the sea or the rain, and then they stand out as prominent 

 buttresses. Detached pinnacles, caverns, and pierced rocks 

 are among the common results of this difference of hardness in 

 the cliff. 



It is not difficult to make out the strata that together com- 

 pose the whole thickness of the cliff between the Causeway and 

 the Pleskin. They are from sixteen to twenty in number, and 

 some of them contain fossils. 



Beyond the Pleskin, as far as Fairhead, the cliff sections, 

 though varying in heights and in some matters of detail, arc, 

 on the whole, of the same nature as those at the Causeway. 

 In many places the chalk, hardened into limestone, stretch out 

 as a white floor level with the sea. 



At one well-known spot, named Carrick-a-Rcde, a wild, 

 rough, irregular rock, altogether detached, and otherwise 



