CHAPTER IX. 



CARBONIFEROUS SYSTEM (continued). 



Trap Rocks of the Clee Hills ; their composition and relations ; effects of their 



eruption. (PI. 30. figs. 6 and 8.) 



The rock which occupies the summits of these hills is, as already stated, a pure 

 basalt. It is indeed of so uniform a structure, that a specimen detached from the 

 Abdon Barf of the Brown Clee Hills, can scarcely be distinguished from one obtained 

 in the Cornbrook or south-eastern extremity of the Titterstone Clee, although these 

 places are about seven miles distant from each other. There are few good natural 

 sections or vertical faces of the basalt, the sides of the hills being encumbered with 

 many large fragments which have fallen from the summits, producing rugged inclined 

 planes. The rock is, perhaps, best exhibited at the culminating point of the Titterstone 

 Clee, called the "Giant's Chair," where it stands out in rude, irregularly-shaped columns 

 (chiefly quadrangular) of four and five feet in diameter and ten to fifteen feet in height, 

 which are crowded together in a confused Cyclopsean pile, as represented in the above 

 wood-cut. Here the columnar shape is the result of joints more or less vertical ; but 

 besides these, there are horizontal laminar divisional planes at right angles to the former, 

 which, when the rock occurs in solid continuous sheets as in Hoar Edge and Cornbrook, 



Q 



