322 GEOLOGY OF BUTE. 



very hard, and has a semivitreous appearance, and thus 

 closely resembles a porphyry. In common with the trap 

 above, and indeed all the beds in this locality, it contains 

 much disseminated iron. The rest of the cliff is occupied 

 by common greenstone or diorite, similar to the lower bed 

 in contact with the sandstone. 



Another bed of lignite occurs on the opposite, or north- 

 west side of the trap district, overlooking Ascog Lake. The 

 coal dips to the interior of the area that is, nearly south. 

 It is of about the same thickness, and is accompanied by 

 beds of steatite and red ochre, very similar to those above 

 described ; but the nature of the ground is such that a com- 

 plete section cannot be had, and the precise number, there- 

 fore, and order of the beds, cannot be exactly stated. The asso- 

 ciation, however, of the lignite with ochres and steatites here 

 also is sufficiently distinct; and it is even probable that these 

 beds are persistent throughout the whole of this district. 



135. In Mull, Skye, and some others of the western isles, and 

 in the basaltic district of the north-east of Ireland, lignites 

 occur in the middle and upper portions of the series, asso- 

 ciated with variegated ochre. The leaf-beds of Antrim, 

 associated with ochre and lignite, discovered by us in 1844, 

 and those of Mull in like association, discovered by the 

 Duke of Argyll in 1850 (without knowledge of our dis- 

 covery), contain the same species of plants. This similarity 

 and that of the beds clearly shew that similar condi- 

 tions have prevailed over a very wide area, the suc- 

 cessive eruptions of igneous matter over the sea bottom 

 being very similar, and that there were like periods of 

 repose, during which the productions of the adjoining land 

 were swept down to be buried under the next flow of sub- 

 marine lava. 



Now, the basaltic series of the north-east of Ireland, as it 

 overlies the chalk formation, clearly belongs to the tertiary 

 era, and was long ago recognized as of this age. But many 

 cases occur in which the same basaltic flow, which alters the 



