338 SKY. GEOLOGY. SECONDARY STRATA. 



which lies to the east of Broadford, but separated from 

 it by an intervening tract of limestone occupying Strath, 

 Pabba, and a small part of its own southern shore, and 

 dividing at the same time that limestone from the corre- 

 sponding one of Rasay. There can be no doubt respecting 

 the identity of the limestone of Pabba, Strath, and Scalpa, 

 or of these with that of Sligachan ; and, as the prolonga- 

 tions of the latter are continuous with the corresponding 

 beds in Rasay, the community of this whole deposit is suffi- 

 ciently confirmed. The nature of the difficulty respecting 

 the position of the sandstone of Scalpa, is examined in 

 another place, and the proposed solution involves that 

 of the small portion of the same rock that lies under the 

 limestone of Sligachan. Now as in Rasay the limestone 

 and its associated shale are traced, by their resemblance 

 and by that of their organic remains, to Scalpa, just as 

 this latter is to the main deposit of Strath, and as in the 

 former they are immediately followed by a great mass 

 of whitish calcareous sandstone, there is reason to con- 

 clude that the corresponding sandstone on the northern 

 shore of Loch Sligachan marks the natural termination of 

 that limestone which has now occupied so large a portion of 

 this account, and the commencement of the last and upper- 

 most strata of Sky, which I must now proceed to describe. 

 These rocks are found in two distinct divisions, widely 

 separated by intervening trap ; the most extensive range 

 occupying the district of Trotternish with a portion of 

 the same shore southwards, and the smallest occurring 

 in the promontory of Strathaird and on the neighbouring 

 point of Swishnish.* 



* Although it appears most probable that both these deposits are 

 parts of the same, and that they both bear a common relation to the 

 gryphite limestone already described, yet as all geologists may not agree 

 in this opinion, I have represented them in the map by different but 

 analogous colours, that I might not prejudge the question : an expedient 

 the more proper since it is not the object of a coloured map to be a sub- 

 stitute for geological description, or an epitome of the scientific relations 



