516 EGO. GEOLOGY. 



it is probable that the intermediate beds of trap are, like 

 those on a larger scale in other places, occasional intrud- 

 ing masses in the form of parallel veins, and that the 

 whole difficulty would be solved if in this as in other 

 instances a perfectly free and continuous access to the 

 .whole series could be obtained. The facility with which 

 the calcareous strata admit of being separated, and the 

 numerous divisions naturally existing between them, will 

 also assist in explaining the peculiar disposition assumed 

 by the intruding trap. 



It is now necessary to inquire into the geological rela- 

 tions of the secondary strata just described. It is evident 

 that no light is thrown on this part of the subject by the 

 history of their connexion with the trap, and Egg presents 

 no appearance of the red sandstone which occurs in Sky 

 and in the neighbouring; island of Rum. There is however 



S O 



no obscurity in their general character, when we consider 

 the organic remains and fragments of coal which they 

 contain, and the resemblance they bear to the uppermost 

 secondary strata of Sky. There is every reason to suppose 

 that they form part of a deposit scattered in an interrupted 

 manner through these islands, and are a portion of the 

 lias series already described. Their connexion with the 

 trap is sufficient to account for their insulated position ; 

 nor is that indeed more remarkable here than in Sky, 

 where the analogous substances are equally separated by 

 masses of trap from each other and from the strata on 

 .which they would otherwise repose. In examining the 

 general connexions of the Trap isles, I shall hereafter 

 take occasion to bring the whole under one comparative 

 view, and thus to supply what may yet be wanting to 

 complete the history of the secondary strata of Egg. 



Such are the appearances and the disposition of the 

 rocks at the north end of this island. The mass of trap, 

 as I have already remarked, extends to the opposite side, 

 where in its dip it excludes from sight the continuation of 

 the stratified rocks which probably lie beneath. In this 



