MULL. GEOLOGY. 57\ 



that every rock with which we are acquainted as forming 

 mountain masses, possessed a peculiar outline and gave 

 a corresponding character to the mountain outlines of 

 a country, so that from these a tolerable conjecture could 

 be formed respecting its composition, it will not be 

 improper to introduce here a few remarks for the purpose 

 of examining into this prevalent notion. The observations 

 that have occurred to me have led to the conclusion, 

 that no general rule can be laid down for any particular 

 class of rock, in which the exceptions will not be found 

 at least as numerous as the examples in favour of it. 

 I would willingly have given plates illustrative of these 

 circumstances, but that a volume would scarcely suffice 

 to place them in a proper manner before the reader. 

 I shall therefore limit these remarks to the enumeration 

 of such instances as are most accessible and best known, 

 confining them at the same time to a few of the most 

 conspicuous rocks. 



The spiry outline of the granite of Switzerland is known 

 to every one, and forms exactly similar are to be seen 

 in the mountains of Arran. Here then is a decided 

 character which the painter recognises and can distin- 

 guish strongly. But the geologist who determines from 

 these instances that every spiry outline implies granite, 

 or that where there is not such an outline, granite does 

 not exist, will be deceived. If in this country he proceeds 

 to Cruachan he will find a simple conical outline, that 

 particular boundary which is so often affected by quartz 

 rock. A step further brings him to the ridge of Cairn 

 gorm. Here is a lumpish form and a smooth rounded 

 line resembling those of the schistose mountains of 

 Wales, and without a single harshness or projection to 

 vary its uninteresting features. Further on, he comes to 

 a land of low undulations, of which if he were to judge 

 from the outline alone, he would conclude that he was 

 surveying a coal field or an undulating mass of secondary 

 strata : yet this is the granite of Aberdeenshire. If 



