103 



grandly up 900 feet above the ridge on which we stand. Though 

 right to the summit "we might press, and not a sigh our toil 

 confess," we must pause now and again to mark the ever-changing 

 features of the magnificent scene gradually opening towards the 

 west and north, and the . new aspects in which the rugged crest of 

 the Ben-Grhnuis range now appears. We must note, too, the change 

 in the rocky floor over which we are passing. We leave the fine- 

 grained granite on gaining the foot of the steep ascent : thence to 

 the summit the mountain is composed wholly of the coarser kind. 

 It is disposed in irregular tabular masses, split up into rhombic or 

 cuboidal forms by fissures, independent of disintegration, and coeval 

 with the solidification of the rock. The thinner masses we have 

 called sheets ; in both the divisional planes separating mass from 

 mass, and the fissures perpendicular to them, are alike the result of 

 crystallization on the large scale, and bear no analogy to stratifica- 

 tion, which is the result of sedimentary deposit. The disintegration 

 of granite, porphyry, and other igneous rocks, is mainly determined 

 by these lines of separation ; in some granites, but more remarkably 

 in porphyry and trap rocks, by the concretionary structure, already 

 referred to in the case of the latter (Art. 31) ; and which has 

 resulted from the mode in which the crystalline centres of affinity 

 develop themselves at the first parting of the heat of fusion, in a 

 melted mass beginning to solidify. The schistose and prismatic 

 forms, under which granite often appears, are but slight modifica- 

 tions of the forms already noticed, depending on the relative position 

 of the divisional planes. The schistose form has often been de- 

 scribed as a true stratification ; but this structure is not continuous 

 in one direction as strata are, nor does it exhibit the fracture or incur- 

 vation of beds ; it is in truth but a local modification of the rhombic 

 or cuboid form, under which granite more frequently appears. 



69. The summit of Cior-Mhor, narrowed by distance into the 

 form of an alpine aiguille, we found to be an irregular elongated 

 plateau, large enough to accommodate a small pic-nic party. The 

 rugged shoulders flanking the peak are huge rifted masses of bare 

 rock, separated by clefts which descend far into the heart of the 

 mountain. On three sides are inaccessible precipices ; the ascent is 

 possible from the west side only. Thrown forward on a salient 

 angle of the western ridge, and little more than 300 feet lower than 

 Goatfell, Cior-Mhor affords a commanding view of the ridges and 

 dividing valleys, the peaks and precipices of this singular mountain 

 group. Its situation as the geographical centre of the tract has 

 been noticed already, and the relations of the various ridges pointed 



