IN THE LOWER OLD RED SANDSTONE OF SCOTLAND. 221
felted vegetable remains. In one or two places (notably Cameron Plantation near Balloch) lenticular patches of anthracitic coal a few lines in thickness have been observed. The flagstones are generally grey, with a more or less distinct greenish tinge, and contain pellets of shale and sparsely scattered lobbies of white quartz. Felspathic and siliceous granules contribute in about equal proportions to the composition of the flagstones. The flags, which are divided by green, grey, blue and purple shales, are extensively used for building- purposes in the neighbourhood (the Duke of Montrose's principal seat, Buchanan House, for example, being built of them), and occa- sionally for pavement, although they are less hard and durable than the Arbroath and Caithness flags. In former days they were fre- quently employed as tilestones ; but this heavy roofing-material has entirely given place to the slates of the Highland border.
We may now shortly trace the flagstone group from the Braes of Doune southwestward to the Clyde.
The fall of the ground from the Braes of Doune to the river Teith at once denudes the flagstone group of the overlying sandstones and conglomerates, so that in the valley the centre of the trough is formed solely by the flagstones. This continues to be the case till the raised beach-deposits of the Carse of Forth to the south of Thornhill obscure the solid geology.
jSouth of the Carse of Forth, the Lower Old Red Sandstone area is rapidly narrowed by the south-westward continuation of the fault which bounds the Ochils on the south side. Extending from Kippen to Cardross Park on the Firth of Clyde, this fault brings, on its south-eastern side, the Calciferous Sandstones down against the Lower Old Red Sandstones. On the south side of the Carse of Forth, brown felspathic sandstones, probably representing those of group B, overlie the Flagstone group, which here dips to the (south- east. The Flagstone group thickens considerably towards the Clyde, and between Geilston and the foot of Loch Lomond (where no other member of the Lower Old Bed Sandstone formation is seen) it cannot be less than 2000 feet in thickness. Here the axial beds of the synclinal trough are concealed by the fault which throws down the Calciferous Sandstones against the Lower Old Red Sandstone. The Lower Old Red Sandstone does not reappear on the southern shore of the Firth of Clyde.
5. Locality. — Quarry, 2| miles S. by "W. of Braendam House, E. of Callander, and S.W. corner of Muir Plantation, near Braendam House.
6. Other Plant-remains. — Fragments of plants have been found in the Lower Old Red Sandstone at the following localities : —
(a) Buchanan-Castle Quarry, near Drymen, Stirlingshire, in a thin- bedded sandstone. A small stem (?), nearly three inches long by two or three lines wide, with portions of the black carbonaceous matter into which it has been converted adhering, and a good deal wrinkled.
(6) Old Quarry at Small Reservoir, near Kilmahew , north of Cardross, Stirlingshire, in a light- coloured thin-bedded sandstone. A stem
