180 Irish Volcanoes. 



sort of coarse paste of chalk, flint, and black rock. Very- 

 marked results are thus observable, identical with those pro- 

 duced by the action of heat, as exemplified in volcanic districts. 



As we advance towards the Causeway, but some distance 

 before reaching it, there is an enlarged crack in the chalk or 

 limestone entirely filled by the black rock. The lava seems to 

 have poured through this and other similar crevices, and, over- 

 flowing at the top, has spread out in a wide flat sheet ; but not 

 only this, large quantities of volcanic ash or scoria have also been 

 erupted, and these have formed an intimate union with the 

 mud of the sea bottom. Thus the lava alternates with this 

 sort of strange paste, in which fragments of chalk and flint 

 have been formed into a pudding, with a natural hydraulic 

 cement or puzzuolana, and this confused mass contains also 

 fragments of hardened lava and of flint. 



In all these cases the black appearance of the basalt con- 

 trasts strongly with the chalk. At the distance of miles one 

 can see the dividing line between the two formations, and as, 

 on the whole, the water acts pretty uniformly on the chalk, 

 while, in the case of the basalt, some parts are excessively 

 hard, others quite rotten, and others again of intermediate 

 condition as to durability, an extremely varied, broken, and 

 irregular coast is the result. 



The constant beating of the sea against the line of cliff from 

 Portrush to Dunluce, has worn the chalk into forms of great 

 variety and beauty — pinnacles, arches, and caverns succeeding 

 rapidly one another, and the effect is much assisted by the 

 striking contrast of the pure white colour of the chalk with 

 the deep velvety black of the basalt. In some places arches 

 are seen above arches, indicating a change of level or some 

 peculiar local cause of decay. Very remarkable among these 

 are the white rocks of Dunluce, marvellously picturesque, and 

 offering much material for geological speculation. 



The small but very neat town of Bush Mills, with its little 

 stream in which thousands of fine salmon are annually caught, 

 lies a little inland from the coast, and the road from Portrush 

 to the Causeway winds round to pass through it. ' 



Over a naked and uninteresting bit of road we make our 

 way from Bush Mills to the Causeway Hotel, a comfortable 

 house of entertainment, yielding all that can be expected in 

 such a locality. Close to the hotel there is a convenient path 

 down a steep cliff to a little bay, from the centre of which 

 the long low Causeway stretches out towards the land of 

 Staffa, where, though at the distance of many miles, a curious 

 repetition of the phenomena exists. It is easy enough to see 

 that it has taken many successive sheets of lava to build 

 up this cliff. The whole from top to bottom is composed 



