146 



huge rolled masses of the rock, is a delightful walk. Near the head 

 of the glen we may diverge a little to the right, and examine, at 

 this lower level, the dike and great chasm descending from Ceim- 

 na-Cailliach. Following it southward on its line of bearing we trace 

 it entering the granite precipices in front of the hase of Cior-Mhor, 

 and passing on over the col, in the direction of the axis of Glen Rosa. 

 The safest pass into this glen is at the western side of the col, or 

 ridge joining Cior-Mhor to the hase of Goatfell. In the hollow up 

 which we pass we have a whin dike beneath our feet, and granite 

 walls on either hand the pathway, in fact, has been formed by the 

 disintegration of this dike. On reaching the summit we observe a 

 great dike, most probably a continuation of this one, ranging right up 

 the front of Cior-Mhor. When one reflects upon the mode of origin 

 of these two rocks, granite and greenstone, it strikes one with 

 wonder to perceive the curious relations which they maintain, and 

 the important part in the physical condition of the region which the 

 dikes play. M. Necker goes so far as to suppose it quite possible 

 that the excavation of Glen Rosa may have been determined by the 

 great dike above noticed. In the lower part of the glen the river 

 runs upon it, between high granite walls, for a long distance 

 (Arts. 64, 65). It is thus by far the most continuous dike yet traced 

 in Arran. 



M. Necker describes a very curious dike as existing on the ridge 

 between the two glens, which we were not so fortunate as to notice 

 in any of our walks this way. " It passes along the ridge between 

 the glens, on the S.E. side of Cior-Mhor, ranging nearly east and 

 west. It consists of five bands; in the middle, there is green 

 pitch stone, on each side of this a band of clay stone porphyry, two 

 feet broad, beyond which are two bands of common trap seven and 

 a-half feet broad each. The dike forms a deep ravine, which 

 reaches to the summit of the mountain. The claystone disappears 

 aloft, and the pitchstone is then five feet broad, and each band 

 of trap four feet ; the band on the north side shows the spheroidal 

 decomposition." (p. 693 of Mem., quoted p. 83.) We noticed no 

 dike on the summit, nor upon the S.W. and western sides ; but 

 it is quite possible it may exist there. 



There is little else of much interest in Glen Rosa; the 

 granite junction has been described already in our first Excursion 

 (Art. 64), and the singular chasm just noticed will be seen as we 

 pass along. The adder (Pelias berus) is often met with in the 

 glen, in places where there is a dry bottom under the heather; and 

 the tourist in crossing these will do well to use caution. Again 



