of the Southern Extremity of Canty re^ Argyllshire. 387 



porphyry. Augitic trap rocks are common, especially in the high 

 ground to the east of Southend church, and associated with the 

 limestone series north of Campbeltown harbour. These rocks are 

 of very different ages, veins of one variety of trap often penetrating 

 beds of another kind, as near Losset and at Kilchousland. At 

 the latter a vein of dark greenstone, divided into columns nearly 

 horizontal, intersects a mass of light grey trap, in some places highly 

 concretionary and divided into verticle columns, separated from each 

 other by thick veins of haematite and green carbonate of copper. In 

 the Laggan of Cantyre west of Campbeltown, a tertiary deposit oc- 

 curs, consisting of peat, with large trunks of trees, covered by beds 

 of red and white clays and gravels. The wood is chiefly oak or 

 birch, and the peat contains leaves of forest trees and hazel nuts. 

 It seems a lacustrine deposit drained during the recent elevation of 

 the land. It rests in the hollows of the red boulder clay with striated 

 blocks, which is in part overlaid by shingle beds, formed of round 

 water-worn stones, gravel, and sand. This deposit much resembles the 

 lignite and drift deposits seen on the coast of Norfolk, and is probably 

 of the same age. The last change of level in the sea and land is 

 marked by a line of cliff surrounding the whole peninsula, and in 

 many places hollowed out into immense caves — some in the hard 

 porphyries of Davar island, measuring 130 feet in length. 



Some of the general results of this investigation seem very inter- 

 esting. The peculiar arenaceous character of the mica slate, inter- 

 mediate between the crystalline rocks of the more northern Highlands, 

 and the silurian beds of the south of Scotland. The amount of lime- 

 stone beds in some parts of the series — the diversity in its dip and 

 direction from the mica slate series in the north, would indicate 

 that this rock belongs to a different group. In a paper read to the 

 Geological Society of London, the author formerly stated that the 

 mica and clay slates on the southern border of the Grampians were 

 probably the northern synclinal of the great trough in which the 

 central coal formation was deposited, and of which the silurian rocks 

 in the south were the other limb. The latter are chiefly of lower 

 silurian age. Hence he concludes that the metamorphic slates of 

 Cantyre are probably altered upper silurian or Devonian beds, and 

 that the great mica slate formation of Scotland will eventually require 

 to be broken up into several divisions. The introduction of the 

 great overlying mass of trap and sandstone into the region coloured 

 by Macculloch as mica slate, renders this part of Cantyre closely 

 analogous to the south of Arran. It also completes the band of 

 igneous rocks, which, commencing on the shore of the German Ocean, 

 near Montrose, is now shown to extend across the whole of Scotland 

 to the Atlantic, and even into the north of Ireland. 



2b2 



