GEOLOGY OF BUTE. 317 



already referred to as encircling the island, it appears that 

 when the sea stood at that ancient level, Bute consisted of 

 four islands, separated by narrow channels. 



Slates and Sandstone. 



The various strata exhibited in Bute are the terminal 

 portions of those great bands of rock, sedimentary and 

 igneous, which extend across the country from sea to sea, as 

 already noticed. Mica slate occupies the northern portion, 

 between the Kyles on the north and Kames and Ettrick 

 Bays on the south. The rock has its usual character and 



Fig. 37. 



a, Kames bay; b, Rothesay ; c, Kilchattan; m, mica slate; n, clay and 

 chlorite slates; s s, red sandstone; t, trap; r, the terrace. 



aspect, and rises into hills of nearly 1000 feet elevation. 

 The district south of this, bounded by the Rothesay valley, 

 consists of the two upper slates, the common clay, and 

 chloritic. Subordinate to these are great beds of quartz 

 rock, the most considerable of which forms the high ridge 

 called Barone Hill, with a picturesque old ruin overlooking 

 Rothesay on the west. There are also copper veins in this 

 slate westwards from Kames Bay. The portion extending 

 from Rothesay Valley to Kilchattau is occupied by red sand- 

 stone; and finally the southern portion, with a substratum 

 of red sandstone, consists mainly of various rocks of the trap 

 family, erupted through and overlying the sandstone. The 

 accompanying outline of the island shews the relation of 

 these strata to the valleys or depressions, which are obviously 

 a part of the system of parallel fractures ranging N.E. and 

 S.W. across Scotland, and probably due to the upheaval of 

 the mountains of the Central Highlands. 



A description of these rocks would be useless, as it would 



