299 



Islay is one of the western islands of Scotland, and was at one time 

 famous as the residence of MacDonald, one of the great kings of the 

 isles. The holds or castles of the MacDonalds exist on islands in 

 some of the fresh-water lakes, to which T shall afterwards allude, espe- 

 cially Loch Gurim and Loch Finlaggan. The extreme length of the 

 island from the Moile of Oe in the south, to Rumhail in the north, is 

 about 30 miles, and its breadth from the point of Ardmore on the east 

 to Sanig in the west, is upwards of 20 miles. The superficial extent 

 is about 154,000 acres, and the extent of coast is nearly 200 miles. 

 The form of the island is irregular, and it is deeply indented by an arm 

 of the sea, called Lochindal. It is chiefly composed of those hypo- 

 gean rocks, termed by Lyell metamorphic, or altered rocks, in conse- 

 quence of the supposed changes which have taken place in them since 

 their deposition. These metamorphic rocks contain few or no orga- 

 nic remains, and are thus separated from the palaeozoic stratified rocks. 

 Clay-slate is looked upon as intermediate between the metamorphic 

 and the fossiliferous strata. The transition, primary, fossiliferous and 

 grauwacke of authors, are considered as belonging to the palaeozoic 

 series, being the strata which contain the fossil remains of the earliest 

 formed animals. The principal part of the island of Islay consists of 

 quartz rock, with beds of clay-slate, grauwacke-slate and micaceous 

 schist. Quartz forms the high grounds of the north, and the great 

 mass of the Oe district. Gneiss occurs in some parts of the island 

 and limestone in others. Porphyritic and basaltic rocks and veins are 

 met with in many places ; the basalt being often of an amygdaloidal 

 nature. Near Portaskaig a peculiar kind of conglomerate occurs. 

 Lead and iron are found in the island, the former being mixed with 

 copper and some silver. At Ballegrant the lead is worked, and the 

 veins are tolerably productive. In the Rhins a vein of magnetic iron 

 ore occurs, which, according to Mr. Campbell, contains a small per 

 centage of titanium. A rich ore of iron is found on Sossit hill, and a 

 vein of iron glance at Ballyneal. At Stramishmore, in the Oe, there 

 is a vein of impure graphite, 200 or 300 feet wide. Mr. Campbell 

 states that he has analysed this, and finds that the quantity of carbon 

 varies from 9 to 60 per cent, and iron from 5 to 16 per cent. He also 

 has detected manganese in small quantity. Dr. R. D. Thomson has 

 examined two specimens of this impure graphite, and the following 

 are the results he has obtained : — 



2 P 2 



