"Vol. 50.] ACID ROCKS OF THE INNER HEBRIDES. 223 



demonstration of this assertion I produce a photograph (PI. XIV.) 

 of the second example (II). The camera, when this view was 

 taken, was planted on the main mass of granophyre which, with its 

 marginal lines of flow-structure and rows of spherulites, could be 

 followed up into the dyke. The vertical walls of the dark-banded 

 gabbros are here clearly exhibited, with the pale dyke of acid rock 

 rising between them. 



But it is not enough to say that the granophyre sends apophyses 

 into the gabbro. The fact of the intrusive character of the acid rock is 

 rendered still more striking by the arrangement of the various beds 

 and veins of the complex mass of basic materials across which the 

 dykes have been intruded. In fig. 1, wherein I have tried to 

 express diagrammatically the parallel banding of the gabbros, it will 

 be seen that the successive basic sheets, dipping in a south-easterly 

 direction at from 20° to 35°, are cut through by the dykes. There 

 is thus a double truncation of the bedding and banding of the 

 gabbros. These structures are abruptly cut off by the vertical wall 

 of the granophyre boss in a general W.N.W. direction, while they 

 are further intersected in a N.N.W. direction by the d} T kes. No 

 more conclusive evidence could be given of the fact that the grano- 

 phyre has been protruded after the last of the successive eruptions 

 of gabbro. 



I have instanced first some cases of apophyses which can actually 

 be seen to diverge from the granophyre mass of Meall Dearg. But 

 there are numerous veins and dykes of exactly similar material 

 which traverse the various rocks of the gabbro ridge, but of which 

 the direct connexion with the main body of the acid rock cannot be 

 observed. These detached portions may be seen all over the ridge, 

 and even on its western front, looking down into the deep hollow of 

 Coire Biabhach. They lie between the dykes I have described and 

 the Druim an Eidhne, where they are frequent, continuing south- 

 ward beyond the Coruisk footpath. Except that they cannot be 

 directly traced to the granophyre and that their visible portions are 

 comparatively short, many of them are in every respect repetitions 

 of the dykes which can be seen to issue from the body of the acid 

 rock. Indeed, it seems to me probable, as above suggested, that 

 some of them are really prolongations of these dykes, rising once 

 more to daylight. But that, in any case, they are true veins or 

 dykes of later date than the basic materials amid which they lie is 

 abundantly manifest from their form, their internal structure, and 

 the manner in which they intersect the surrounding rocks. 



These detached masses are long aud narrow strips, like the dykes 

 just described. They vary up to 6 or 8 feet in breadth, and can be 

 followed continuously for variable distances, often for 20 feet or 

 more. They display, exactly as the dykes do, a fine-grained texture, 

 beautiful flow-structure, and rows of spherulites. Moreover, the 

 flow-lines follow faithfully the irregularities of the bounding walls 

 of gabbro, curving round projections with the sweeping and some- 

 times curling lines so characteristic of rhyolitic streams. Nowhere, 



