On the Old Red Sandstone of the South of Scotland. 287 
Stonehaven and Strathearn, including the south-eastern flanks of 
the Grampians for about two-thirds of their course. Metamorphic 
rocks, trap-rocks, the Lower and Middle members of the Old Red 
Series (the former being sandstone, and the latter conglomerate), 
are the constituent rock-masses of the district, and give it its pecu- 
liar physical features. ‘The mode in which these rocks are associated 
is well exhibited in the section on the coast (at Stonehaven), and in 
the several sections in the interior where streams lay bare the rocks. 
Sections at Stonehaven, Glenburnie, Strathfinlass, North Esk, West 
Water of Lithnot, Cruick Water, South Esk and Prosen, Blairgowrie, 
Dunkeld, Strathearn, and Glenartney, were described in detail. 
Against the nearly vertical, but somewhat north-westerly dipping, 
_metamorphic schists (which sometimes include conformable lime- 
stones), come purple flagstone, but usually separated from them by 
trap-rocks, having the same strike. These flagstones pitch to the 
south-east, but retain a high angle away from the schists, and, in 
many places, are intercalated with beds of trap. The lower purple 
flagstones are unfossiliferous; but higher up tracks of Crustaceans 
(Protichnites) have been discovered by the Rey. H. Mitchell. The 
grey fossiliferous flagstones of Forfarshire succeed, still with a steep 
dip. Conglomerates succeed, in beds having a less inclination, 
gradually becoming more and more horizontal as they reach the low 
country. 
The axis of the elevation of the Grampians thus appears to be 
along their southern margin, and to be marked by the trap-rocks 
separating the metamorphic schists and the purple flagstones of the 
Old Red series, and giving the latter their general south-easterly 
dip. As the metamorphic rocks of the Grampians have not yielded 
any fossils, their relation to the other old rocks of Scotland is diffi- 
cult to determine. 
3. “On the Old Red Sandstone of the South of Scotland.” By 
Archibald Geikie, Esq., F.G.S., of the Geological Survey of Great 
Britain. 
This paper was the result of a series of explorations carried on at 
intervals from Girvan to St. Abb’s Head. The first part related to 
the geology of the border-district of Lanark and Ayr, near Lesma- 
hagow. ‘The Silurians and Lower Old Red sandstones of that 
district, as formerly pointed out by Sir Roderick Murchison, form 
one consecutive series. ‘They are traversed by great numbers of 
felstone-dykes, and are disposed in longitudinal folds, ranging from 
N.E. to 5.W.., the Silurian strata forming the axis of each anticline. 
Both series are overlaid unconformably by Carboniferous strata 
belonging to the horizon of the Mountain Limestone group of 
Scotland. ‘The features of this unconformity are well displayed all 
round Lesmahagow, where an enormous series of Lower Old Red 
sandstones, more than 10,000 feet thick, have their truncated edges 
overlapped by gently inclined beds of Carboniferous sandstone, shale, 
and limestone. ‘The whole of the Lower Carboniferous group and 
the upper Old Red Sandstone, amounting in all to at least 6000 or 
