﻿Jan. 8, 1851.] duke of Argyll on ardtun leaf-beds. 91 



western coast, and visible from a great distance among the Hebrides. 

 These mountains are raised far above the highest level to which the 

 traps of the island attain. A portion of it is coloured by Macculloch 

 as syenite, and specimens in my possession from the Peak of Ben 

 More belong to this class of rock. But the whole of the long and 

 high promontory stretching westward from the flank of Ben More, 

 and lying between Loch na Kael and Loch Scridden, exhibits great 

 terraces of trap, piled one above the other, and terminates in that 

 striking headland of Bourg or Gribon, whose lofty horizontal lines 

 rise from the ocean with almost perfect regularity in a pyramidal 

 form, until the final cap attains an elevation of about 2000 feet. 



The southern division has been long known for the magnificent 

 coast scenery it displays ; presenting a continuous line of mural pre- 

 cipices of great elevation, frequently based on and capped by basalts 

 of every variety of form, and including extensive strata of the oolite 

 and lias. Sections of this coast have been given by Macculloch* and 

 by Sir R. I. Murchisonf. 



This division is prolonged considerably farther towards the west 

 than the other two, ending in the long promontory called the Ross. 

 The same geological character, however, is not preserved throughout. 

 At a point nearly opposite to the headland of Bourg, the trap ter- 

 races of this division likewise descend, but less abruptly, to a lower 

 level. An interval of mica slate succeeds ; and the remainder of the 

 Ross consists of low round hills, entirely composed of a fine hard red 

 granite. 



Along the line of junction between the trap and mica slate, the Ross 

 is indented in a direction nearly north and south by a deep bay or arm 

 of the sea, called Loch Laigh. The head of this bay is mica slate, 

 the western side is granite, whilst the eastern is a prolongation of the 

 last and lowest of the trap terraces — the last, I here mean, in the 

 westerly direction, but, as it now appears, the last also probably in 

 respect to age. In most other situations the headland of Ardtun, 

 the termination of this terrace, would have attracted prominent at- 

 tention ; but its basaltic columns, although very perfect and beauti- 

 ful, are small when compared with those wonderful pillars, which in 

 the same landscape are seen bending round the cave of Staffa, whilst 

 in height it seems an insignificant cliff upon a line of coast marked 

 by the towering precipices of the Inimore of Carsaig and the lofty 

 terraces of Bourg. 



The first public mention I can find of the headland of Ardtun is 

 from the pen of Dr. Samuel Johnson. Sir Allan M c Lean, in con- 

 veying him from the island of Inch Kenneth to visit the ruins of 

 Iona, selected this spot as a resting-place ; and the Doctor mentions 

 that its columnar basalt, on whose broken shafts they sat, was pointed 

 out to him as scarcely less deserving of notice than that of Staffa. 

 This was in 1 773, and the visit of Sir Joseph Banks in the previous 



* Description of the Western Islands of Scotland, &c. 1819, vol. i. pp. 559, 

 561 ; and vol. iii. pi. 20. fig. 11. 

 f Trans. Geol. Soc, 2nd Series, vol. ii. Pt. 3. p. 359. pi. 35. 



h 2 



