208 



JURA. GEOLOGV. 



direction of the whole mass of strata, as in Scarba 

 and Lunga, and in the Slate isles ; nor even to determine 

 the predominant one. At the northernmost end of the 

 island it is evidently continuous with that of the two 

 islands just named, that is, N. half E. ; but at the 

 southern extremity it appears to become even more 

 easterly than in the mountain above described ; following, 

 apparently, both here and in Isla, the direction of the 

 northern part of the Slate isles, namely, N. E. by W. 

 A similar flexure will therefore be found in Jura to 

 that which occurs in Luing; and the great body of 

 strata, here as in Isla, will probably be found conformable 

 to the general direction of the primary stratified rocks 

 on the mainland. The north-easterly direction appears 

 to be the prevailing one, and the northerly but a 

 temporary and limited deviation. It will immediately 

 appear, on inspection of the map, that the outlines of 

 the coast indicate such a direction of the strata; but 

 I cannot speak with confidence of the bearings there 

 laid down, as they are by no means easy to determine. 

 In describing the details of this rock and its accom- 

 panying strata, I shall commence with the central line 

 of the island, as being the most simple, and as a point 

 of constant reference for the rest. 



This line, which forms the main body of the island, 

 consists entirely of quartz rock. In various places, beds 

 of micaceous schist, and of different conglomerates which 

 are not strictly quartzose, are intermixed with it; but 

 they are both of rare occurrence and in small quan- 

 tity ; the greater masses of these rocks being found 

 on the eastern skirts of the island, or towards the 

 upper surface of the great quartz beds. The thinner 

 beds occur in different parts of the mountains, in Ben 

 an oir, in Ben na caillich, and in Ben shianta, where 

 their alternations with the quartz rock are evident ; 

 but they are even more numerous and more accessible 

 in the northern and lower range of hills which reaches 



