IONA. GEOLOGY. 21 



The gneiss of lona is by no means abundant in granite 

 veins. A few, however, but those of a small size, may 

 be seen towards the middle and north end of the island. 

 Here the schistus entirely vanishes and the rocks as- 

 sume the more decided character of gneiss. At the same 

 time, the regular disposition of the beds is much dis- 

 turbed, or disappears altogether. I observed no other 

 granite in the island than these veins and that rock near 

 the Bay of Martyrs described at the beginning of this 

 sketch. 



One porphyry vein may be seen traversing the gneiss 

 in a small bay situated between the marble rock and 

 Port na Curachan. It runs in a S. S. W. direction, dipping 

 about 35 degrees, and is seven feet in thickness. It 

 contains both mica and hornblende, imbedded together 

 with felspar crystals in the common base of compact 

 felspar. If there are any other veins of this description 

 they escaped my observation. 



Only one other rock occurred to vary the uniformly 

 tedious recurrence of the gneiss, and this is situated 

 in the interior not far from Bloody Bay. It is a lime- 

 stone, containing both mica and noble serpentine distri- 

 buted through it in minute spots, in such quantity as 

 nearly to overpower the calcareous base. It is a stone 

 of extraordinary toughness. 



Whatever minerals lona may still possess concealed 

 among its wearisome rocks, they remain to reward the 

 toils of some future geologist. I shall scarcely visit it 

 again, having fulfilled the Gaelic proverb, which in verse 

 not less rude than the translation, asserts that 



There never yet came man to I* 

 Who did not come times three. 



* I, (tar e^o^v), the Island, from the religious veneration attached 

 to it. lona I-thona; the Island of Waves. I-Columb-kil ; the 

 Island of Columba's Cell. 



