SKY. GEOLOGY. SECONDARY STRATA. 333 



where conspicuous for the rapidity of its decomposition. 

 It may therefore have existed in many places where it is 

 now no longer to be seen ; while, from its intersecting 

 and venous disposition, it may even now exist below 

 the surface in many places where it is not visible. That 

 the effect in question does not appear in every place 

 where the syenite is actually in contact with the lime- 

 stone, is no proof against this supposition; the negative 

 in these cases being inefficient where all the accompany- 

 ing circumstances are unknown. The same reasoning 

 applies to the effects produced by trap veins on the 

 adjacent rocks, which are equally uncertain; while their 

 frequent influence in changing the calcareous rocks which 

 they traverse, from an earthy to a crystalline state, pre- 

 sents an analogy so strong as necessarily to suggest 

 itself to eveiy geologist. The phenomena that attend 

 the passage of these veins through the indurated chalk 

 of Ireland, are in this view particularly worthy of notice. 



I shall hereafter have an opportunity of adding some 

 analogies to these arguments, in the account of the circum- 

 stances that attend the limestone of the Isle of Man ; 

 to which article I shall refer the reader and now proceed 

 to examine the remaining detached portions of this rock 

 that occur in Sky. 



The first of these is found on the south-eastern shore 

 of Loch Eishort at Ord, and although thus separated 

 by the whole breadth of the water at this place, from 

 the principal mass on the north-western side of that loch, 

 the separation is more apparent than real ; since the inter- 

 mediate islets, as well as the numerous sunk rocks, consist 

 of the calcareous strata already described ; thus establish- 

 ing their continuity between both shores. The space 

 occupied by the limestone* on the shore of Ord seems 

 to exceed a mile in length, and its total extent may be 

 conjectured with some probability, both from the form of 

 the hill which it there skirts, and from the superiority of 

 the vegetation in that spot ; from both which indications, 



