128 Dr. Mac Culloch's observations 



I shall continue to describe this rock as far as I have traced it r 

 since if not strictly a part of the professed object of this paper, it 

 will, in addition to the contribution which it forms to the mineral 

 topography of the country, either assist future geologists in con- 

 necting their own observations, or present them, in a tract among 

 the most desert and difficult of access in Scotland, with a point of 

 departure from whence they may prolong their observations over 

 the adjoining country. 



In leaving Balahulish to proceed westward we almost imme- 

 diately lose sight of the granite, which occupies here only the lowest 

 position, and is scarcely to be found above the level of the sea. 

 The schistose rocks which cover it do not however accompany us 

 long, being succeeded at the mouth of Glenco by a mass of rocks 

 appertaining to the porphyry family, which I shall recur to when 

 I have traced the granite. This becomes again visible as we ap- 

 proach the King's house, and, quitting the rugged hills which 

 separate Glenco from Loch Etive and from Loch Leven, enter 

 upon the wide, trackless, and solitary moor of Rannoch. This 

 extensive and barren tract is elevated at a very considerable height 

 above the sea, and, although unascertained, it probably does not 

 fall much short of a thousand feet. Its surface in a general sense is 

 flat, when compared with the ordinary aspect of a Highland moor, 

 yet it is diversified by low rocky hills and undulations, covered 

 with a deep peat which conceals the subjacent rock. There are 

 notwithstanding abundant indications of its nature in the beds of 

 the streams which flow over it, by which the naked rock is com- 

 pletely exposed to view, while every protuberance which time or 

 accident has laid bare, and the detached blocks that are strewed over 

 its surface, confirm its identity with the granite of Glenco. It can 

 be thus traced to the head of Loch Rannoch, a distance estimated 



