FLAN NAN ISLES. GEOLOGY. 199 



the ancient ecclesiastical compositions which abound in 

 a perpetual recurrence of fugue and imitation on a few 

 simple notes. It requires no effort of imagination to 

 trace the sound of the flute, the hautboy, and the bassoon, 

 in the cries of the several birds ; the upper parts being 

 maintained by the terns and the gulls, the tenors by 

 the auk tribe, while the basses are occasionally sounded 

 by the cormorants. The cultivated musician will, inde- 

 pendently of the general effect, derive pleasure from 

 the perpetual repetition and the apparently perfect reso- 

 lution of the discords; while the whole is varied by the 

 pauses which are occasionally interposed, and by the 

 swelling of the sounds on the breeze ; or by their alternate 

 increase and diminution as the alarm subsides and is 

 again renewed. 



These islands are bounded all round by cliffs cut sharply 

 down to the sea, and almost all bearing the marks of 

 recent fracture and separation ; an appearance arising 

 from the little wearing which they undergo from atmo- 

 spheric action, and from the obstinacy with which they 

 seem to resist the growth of lichens. They afford, in 

 consequence, rocky scenery of considerable grandeur; 

 the effect being enhanced by the very circumstance 

 now noticed, the marks of force still strongly impressed on 

 them, as if the moment of their separation and ruin 

 were but just passed before the spectator's eyes. Their 

 average height appears to be about 100 feet. 



As they do not seem to have been surveyed, they 

 are an object of terror to mariners intending to pass 

 round the Butt of the Lewis, their situation only being 

 marked in the sea-charts. That terror is misplaced. 

 Two detached rocks only, lie to the westward, but they 

 are both visible at high water, and with this exception, 

 a ship may range them safely at half a cable's length ; 

 since they are free from sunk rocks and the water is of 

 j>;reut depth. 



