386 Professor James Nicol's Notes on the Geology 



cept in some incidental remarks in the works of Professor Jameson 

 and Dr Macculloch. 



The oldest or fundamental rock of the district examined is mica 

 slate, forming the wild country round the Mull of Canty re, the moun- 

 tain Bengollion, near Campbeltown, and the high ground north of 

 that town. It is generally a light grey arenaceous rock, often more 

 resembling a micaceous sandstone than the typical mica slate of the 

 northern Highlands. The beds are also less contorted, and dip 

 at a low angle, or about 30° on an average, to the east, or a few 

 degrees south of east. Occasionally it is connected with a dark- 

 coloured large-granular crystalline limestone in numerous beds. In 

 Knock Scalbert, north of Campbeltown, this limestone series seems to 

 differ in direction from the mica slate, the beds running NE. by N., 

 and hence may probably form a distinct, perhaps newer part of the 

 series. The primary rocks are followed by red sandstone and con- 

 glomerate which often rest almost conformably on the older strata. 

 This is seen in Knock Scalbert, on the north shore of the harbour, 

 very markedly in Glenramskill Burn, and at the south of the penin- 

 sula near Keills. In all these places the dip and direction of the 

 two formations approximate as closely as that of the separate beds of 

 each. The conglomerate is often of immense thickness, and consists 

 of rounded blocks, varying from three feet or more to a ^qw lines in 

 diameter, imbedded in a red sandy basis. The blocks have a very 

 local character, being in some places almost exclusively a clove-brow^n 

 porphyry — in others hard sandstone or hornstone — in others quartz or 

 trap rocks. It is remarkable that no fragments of the mica slate on 

 which they rest, or of other primary rocks, were observed in these con- 

 glomerates. The red sandstone, especially on the east and south-east 

 coast, is often almost a tufa, composed of the same materials with the 

 claystone porphyries, with which it is, in part at least, contempor- 

 aneous. The coal formation occurs chiefly to the west of Camp- 

 beltown, in the low tract named the Laggan of Cantyre. The 

 true character of this formation, as a detached portion of the 

 central coal-field of Scotland, was pointed out by Professor Jameson 

 in his travels in Scotland. Dr Macculloch, in his Western Isles, seems 

 to have adopted the same opinion, but afterwards in his map coloured 

 it as lias. The impressions of Lepido-dendron, Sigillaria, Stig- 

 maria, and other plants found in the coal, and in the connected shales 

 and sandstones, prove its true age, and no trace whatever of the lias 

 has been found in this part of Scotland. The coal deposits are 

 broken through by dykes of trap, and are also overlaid by igneous 

 rocks on the shore near Losset and in Tirfergus burn. The igneous 

 rocks are principally claystone and felspar porphyries, which form a 

 broad band across the country from Kilkivan and Losset on the 

 west, to Macharioch on the east, in the region coloured by Mac- 

 culloch as mica slate. In this tract fragments of altered limestone 

 and sandstone of the coal formation often occur, imbedded in the 



