118 KERRERA. GEOLOGY. 



of the strata that precede and follow it. The origin of 

 this confusion must be sought in those causes which 

 so often affect the regularity of stratified rocks where 

 extensive masses or numerous veins of trap occur. 



It will often appear on examination, that the conglo- 

 merate lies above the simple trap as well as below it; 

 and perhaps this order does actually take place. If it 

 is sometimes seen lying below the clay slate, it will, I 

 doubt not, be found that this is a deception arising from 

 the mechanical derangement of the respective rocks ; and 

 that superior altitude is not in this case a test of superior 

 position. It is a remarkable proof of such derangement, 

 that the highest summit of the island is formed of con- 

 glomerate accompanied laterally by hills of clay slate 

 little less elevated; while again, on the shore, and par- 

 ticularly at the south-westem end of the island, the same 

 rock presents a remarkably regular series of beds not 

 materially deviating from the horizontal position. These 

 regular beds dip toward the west wherever they can be 

 examined ; and they are therefore here, as in Inish Capel, 

 placed in a reverse position to the primary strata. The 

 same is true of those partially exposed masses of red 

 sandstone which are found on the adjacent mainland. 

 But the considerations arising out of this must be de- 

 ferred to a more proper place. 



I must not however quit this subject without stating 

 the reasons for supposing that the conglomerate and 

 sandstone series of Kerrera and the neighbouring shore, 

 is analogous to that which, in the other parts of this 

 country, separates the primary from the secondary strata. 

 The only differences indeed, are its broken and inter- 

 rupted position, and the nature of its materials. The 

 peculiarity of position is partly to be accounted for by 

 the ordinary waste which all rocks undergo, according 

 to their several degrees of tenacity and exposure ; and 

 partly, perhaps still more, by the great number of trap 

 veins which traverse it, and the great extent of overlying 



