﻿I860.] 



JAMIESON- 



r S.W. HIGHLANDS. 



137 



mica also becomes less ; and the great body of the rocks along the 

 very clear section of the west shore from Kilmichael to Kilda- 

 vannan Point, where the slates commence (a distance of about three 

 miles), is found to be highly silieeous, often almost wholly of quartz ; 

 they are in fact altered sandstones, varying in quality from fine grit 

 to coarse indurated sand with grains of the size of peas or beans, 

 in which the water- worn character still remains quite distinct ; 

 nothing, however, so coarse as to be termed a conglomerate oc- 

 curred. These siliceous beds vary in colour, but are for the most 

 part of a pale greenish-grey. Although no decided beds of slate are 

 met with along this part of the section, yet there are some nests and 

 patches of fine sediment, and even a few thin seams here and there, 

 precisely similar in quality to the material of the thick beds of slate 

 that follow. These slates commence, as I have said, at Kildavannan 

 Point on the west, and at Ardmaleish Point on the east shore of 

 Bute, there being frequent alternations of grit and slate where they 

 first make their appearance. Near the base of these slates at Kilda- 

 vannan Point I found some arenacous beds composed of exceedingly 

 fine yellowish-green sand, often parted by seams of white sand, all 

 laminated in the most delicate manner, and even showing indications 

 of false-bedding; they also alternate with coarser-grained layers 

 similar in quality to the underlying grits. 



The great mass of slates that follow consists of finely laminated 

 sediments, generally of a greenish colour, but containing also many 

 seams of dark-blue roofing-slate : these blue slates are not exclu- 

 sively confined to any one part of the series, being found in every 

 portion of this division; but they are perhaps most frequent near the 

 base and top. Many alternations of dark-blue and green slate are 

 seen. I am led to notice this the more as the late Daniel Sharpe, 

 in his paper on the Southern Border of the Highlands (Quart. Journ. 

 Geol. Soc. vol. viii. p. 127), had distinguished them into two sepa- 

 rate formations, which he termed the dark-blue and the chloritic or 

 green slates, — a distinction perhaps correctly descriptive of some 

 localities, but evidently not of general application. These thin- 

 bedded sediments form a zone across Bute, extending on the west 

 side from Kildavannan Point to a place called Mecknoch, a short 

 distance to the north of Ardscalpsie Point, and on the east side 

 from Ardmaleish Point to Rothesay Bay. They vary in quality from 

 the finest clay-slate to slaty flag and thin-bedded grit ; and there 

 are even a few seams of coarse-grained grit, with grains of the size 

 of peas or beans. Intercalated seams of mica-slate are also met 

 with. The colour is various, from dark purplish-blue to pale green, 

 silvery-grey, and brown ; but the prevailing hue is greenish, and 

 the rock is thinly laminated. They had been the finely comminuted 

 sediment, the silty mud and clay, of the old sea-bottom, the grits 

 being the sand and gravel. So far as I noticed, the fines of deposition 

 are almost always quite distinct, being seldom obscured by cleavage. 



Covering these thin-bedded slates I found a thick mass of grit, 

 forming a rugged hilly ridge stretching from Ardscalpsie Point to 

 Barone Park nearBothesay, and of which Barone Hill attains a height 



