572 31ULL. GEOLOGT. 



we resume the spiry outline once more, we shall find 

 the Cuchullin Lills marked by a high and strongly 

 serrated boundary, rising into spires and pinnacles more 

 lofty and rugged than those of Arran ; and here the 

 geologist is surveying the picturesque forms of trap. 

 Even the breccia of Montserrat presents similar cha- 

 racters, exceeding in decision those already enumerated. 



But the mountains of Sky afford examples also of the 

 outline most contrasted to the former, smooth, round, 

 and undulating. These are formed of a different mem- 

 ber of the trap family ; while the same rocks in Mull tend 

 to the simple conical shape, and in Arran subside into 

 gentle undulations not to be distinguished from the out- 

 lines of Radnorshire, or the swelling and flowing lines 

 of Dartmoor. 



Hills of quartz rock are generally characterized by the 

 simple conical outline. Yet there are many exceptions 

 to this rule. Although true in Jura and in Assynt, it 

 does not hold good in Ben Gloe, where the outline is 

 rounded; the eye being unable to distinguish by their 

 picturesque features, the summits of quartz rock from 

 the neighbouring hills of granite. It is unnecessary to 

 detail the forms assumed by micaceous schist, since, among 

 the infinite varieties of this rock, examples of deviation 

 from any imaginary standard may be seen all over Scot- 

 land ; from the serrated summits of Cowal and Ben Venu 

 to the conical elevations of Ben Lomond and Ben more, 

 and the undulations of Knapdale and Cantyre. The same 

 remarks might be made on gneiss, but they are rendered 

 unnecessary by the description of this rock already given 

 in a preceding article. The southern division of Scotland 

 is in itself a sufficient example of the fallacy of such a 

 rule. Almost uniformly undulating over a large tract, 

 without the slightest variation of character on which the 

 expressive touch of a painter can rest, the geologist 

 finds it to contain sandstone, trap, schist, porphyry, and 

 granite. 



