﻿142 PROCEEDINGS OE THE GEOLOGICAL SOCIETY. [Dec. 19, 



verted from a quartz-grit into compact jasper-like or hornstone- 

 quartz. The greenstone itself is likewise affected, and traversed by 

 some very odd veins of quartz, which seem to proceed out of the 

 sedimentary rock. Yarious thinner beds of greenstone are seen 

 near these, interstratihed with the quartz-rock and following its 

 undulations. Between Inverneil and Loch-Gilphead I noticed in- 

 stances where layers of mica-slate, followed along their strike, may 

 be seen gradually to assume a greenstone aspect ; these micaceous 

 strata are also often much contorted in the neighbourhood of the 

 greenstone, which is itself occasionally altered and traversed by 

 cream-coloured veins. The action of the greenstone upon the thin- 

 bedded slates may be noticed in the low masses along the shore 

 near Ardrishaig Hotel. Sometimes it has caused a segregation of 

 the mineral ingredients, the quartz forming numerous white streaks 

 parallel to the bedding, together with some larger veins ramifying 

 in a more irregular manner ; carbonate of lime has also in some 

 cases segregated along with the quartz ; while the chlorite has also 

 in a great measure been purged of its impiirities, forming a tough 

 mass which has quite lost its laminated fissile character, and in 

 some cases it appears to pass insensibly into the greenstone. 

 Although neither here nor elsewhere did I notice veins ramifying 

 from the greenstone, yet it has in some cases burst through the 

 strata transverse to the bedding, in good-sized masses. An instance 

 of this may be seen on the shore about halfway between Ardrishaig 

 and Loch-Gilphead, near a place marked Glenburn in the Admiralty 

 Chart, where some greenstone has protruded across the green slaty 

 strata, which become much crumpled as they approach it, and 

 assume an irregular sort of cleavage, or cross-planes of division ; they 

 also become more micaceous ; and at some points the prolongation 

 of these micaceous slates passes insensibly into the greenstone 

 without any clear line of separation ; there is, in short, a gradual 

 conversion of the slate into a massive greenstone ; but in other parts 

 the line of meeting is easily seen. 



On the shore of Loch Fyne, to the north of Otter Ferry, near 

 a place marked Gortans in the Admiralty Chart, where green- 

 stone has invaded the quartz-strata and caused much alteration and 

 contortion in them, I observed a curious change in the greenstone 

 itself near its contact with the quartz, whereby it assumed a foli- 

 ated structure, and became highly micaceous — in short, took on the 

 aspect of a greenish mica-schist to the thickness of one or two 

 feet. 



I observed likewise instances, both in Bute and Knapdale, where 

 dark fissile clay-slate is changed, near its contact with greenstone, 

 into a substance like basalt. On the line of the Crinan Canal, 

 between Dunartry and Ballenoch, a mass of greenstone is con- 

 spicuously seen, the weathered surface of which is full of circular 

 concretions like those often noticed in decomposing trap. 



The chlorite-series has been laid down in the map of Macculloch 

 only in Argyleshire ; this geologist therefore seems to have regarded 

 it as distinct from any of the other Scottish formations. Under 



