52 



hence we may call the rock a calcareous amygdaloid. The upper 

 portion of this bed, to the thickness of a few inches only, is 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 greenstone, 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 complete section cannot be had, and the precise number, 

 therefore, and order of the beds cannot be exactly stated. The 

 association, 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. It is to these 

 ochreous and steatitic beds that Dr. MacCulloch refers when he says 

 that he "has met with no similar substance among the numerous 

 trap rocks examined in the course of the survey of the Western 

 Islands." He has not indeed described any such strata ; yet casual 

 mention is made (vol. i., p. 376) of an iron clay and jaspery substance, 

 forming extensive beds in the trap of the cliffs of Talisker in Skye 

 the same in which the lignite also occurs and that these are 

 often variegated with red, gray, and purple colours. No further 

 description is given, nor is the precise position of the lignite men- 

 tioned, ttie cliffs being of very difficult access. 



But even by such a brief notice the steatitic beds and variegated 

 ochres are easily recognized; and though these characters are not 

 very distinctly marked in the beds we have been describing in Bute, 

 yet they apply exactly to the red and variegated ochres, which 

 occur as members of the trap series of the north-east of Ireland. 

 The trap rocks there cover an area of upwards of 1,000 square miles, 

 and vary in thickness from 300 to 1,200 feet. They repose upon 

 chalk, while the Scottish series rests on the old red sandstone and 

 coal strata. In the Irish series the lignites occur in the middle 

 and upper parts, associated with variegated ochre and basalt. There 

 is, as we have seen, a like association in Bute. The interesting 

 leaf-beds and associated lignites, overlaid by trap in Mull, discovered 

 and described by the Duke of Argyle (Jour. Geol. Soc., 1851), 

 seem to be a deposit precisely analogous to the Antrim and Bute 

 lignites ; and from the casual observations of Dr. MacCulloch it 



