252 ISLA. GEOLOGY. 



larity of the substances in both, and by the corre- 

 spondence in their positions and in the order of their 

 succession; while the rarity of the substances in question, 

 which are no where else to be seen in these islands, tends 

 still further to confirm this view. It is not however 

 necessary, as already suggested, to imagine that they 

 are absolutely continuous and of the same dimensions 

 throughout ; the well known attenuations to which strata 

 are subject, may here exist without materially disturbing 

 the general conclusion now drawn. The strata of Lossit 

 hill will thus assume their regular situation in the series 

 which forms Isla ; and will be found to alternate, according 

 to the order of succession already established, with those 

 rocks that possess the greatest degree of regularity; being 

 bounded on both sides by the various alternations of 

 the schists and quartz rock already described. Thus 

 also the geological structure of this chain of islands may 

 in a great measure be completed ; since it is probable 

 that the schistose strata, which form the mass of Isla 

 to the eastward, are prolonged under the usual variations 

 arising from alternate dilatation and extenuation till they 

 meet with the intruding trap of Mull. Garveloch will 

 thus also appear no longer an independent and anomalous 

 mass, but part of a regular series; remaining insulated 

 in the sea, a beacon to indicate the system of order 

 which pervades the whole. 



A similar analogy may be extended to the blue lime- 

 stone first mentioned, by comparing it with that of 

 Lismore, an island which will shortly be described.* The 

 general bearing of that island and of its strata, will be 

 shown to be nearly parallel to that of the northern portion 

 of Luing, and to those of Garveloch and Seil, namely, 

 N. E. by N. or somewhat more easterly. It is not possible 

 however to establish here even the same limited appear- 

 ance of continuity as in the former instance ; since that is 



* See the general Map. 



