FULPrr ROCKS 2 1 



more solemnizincr influences than come to their brethren of 

 the inland countr\- who dwell amid milder conditions. 



The circumstances which lead to the formation of these 

 curious detachments of rock from the parent cliff are sub- 

 stantially as follows : The shore precipice being rent by 

 numerous crevices or joints, it here and there happens that 

 these lines of weakness lie in such positions that they in- 

 tersect each other as the excavation is pushed into the land. 

 Working, as we have seen the waves do, more efificienti}' in 

 these recesses than on the smooth cliffs, the intervening mass 

 of the steep does not recede so rapidl)-, and so is left as an 

 outlying fragment around which the sea washes at low tide. 

 The observer will note that in general these pulpit rocks 

 have a prow-like projection turned toward the shore. This 

 shape is due to the fact that the joints or other lines along 

 which the waves work, intersect each other so as to form 

 the wedge-shaped block which in time becomes detached. 

 One of the most ordinary causes of the peculiar wearing 

 which we have to note here arises from the crossing of 

 dykes, or fissures filled with hardened lava, which, like that 

 thrown out by volcanoes, was once molten. These dyke- 

 stones are often composed of very fissured rock which the 

 waves easily disrupt and bear away : it often happens indeed 

 that the material resembles a mass of billets of wood heaped 

 closely together, as in the case of the Giant's Causeway of 

 northern Ireland. When frost acts with vigor, as it does 

 along most of the shores where the pulpit-rock structure 

 occurs, its effect is greath' to aid the surges in rending away 

 these dyke-stones, while it may have very little influence on 

 the more compact parts of the cliff. 



The action of freezinof and of frozen water along all cliff 



