380 
THE GEOLOGIST. 
and Strailiearn, including the south-eastern flanks of tlie Grampians for about 
two-thirds of their course. Mrtaniorphic rocks, trap-rocks, the Lower and 
Middle members of the Old lied Series (the former being sandstone, and the 
latter eon"'lomerate), are tiie constituent rock-masses of the district, and give 
it its peciiliar 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 Stone- 
haven, Glenburnie, Strathfinlass, North Esk, West Water of Lithnot, Cruick 
Water, South Esk and Prosen, Blairgowrie, Dunkeld, Strathearn, and Glen- 
artney, were described in detail. 
Against the nearly vertical, but somewhat north-westerly dipping, mcta- 
morphic schists (which sometimes include conformable limestones), come purple 
flagstones, but usually separated from them by trajj-rocks, having the same 
strike. These flagstones pitch to the south-east, but retain a high angle away 
from the schists, and, in many jilaces, are intercalated with beds of trap. 
The lower purple flagstones are uufossiliferous ; but higher up tracks of Crus- 
taceans (Frotichnites) have been discovered by the Kev. 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 meta- 
morphie schists and the purple flagstones of the Old Red series, and giving the 
latter their general south-easterly dip. As the metamorfihic rocks of the Gram- 
pians have not yielded any fossils, their relation to the other old rocks of 
Scotland is difiieiilt to determine. 
3. " On the Old Red Sandstone of the South of Scotland." By Arcliibald 
Geikic, Esq., E.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 Lesmahagow. The Silurians and 
Lower Old Red sandstones of that district, as formerly pointed out by Sir 
Roderick Murehison, form one consecutive series. They arc traversed by 
great numbers of felstone-dykes, and are disposed in longitudinal folds, ranging 
from north-east to south-west, the Silurian strata forming the axis of each 
anticline. Both series are overlaid uuconformably 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 ten thousand feet 
thick, have their truncated edges overlapped by gently inclined beds of Car- 
boniferous sandstone, shale, and limestone. The whole of the Lower Carboni- 
ferous group and the upper Old Red Sandstone, amounting in all to at least 
six thousand or eight thousand feet, are here wanting. But as the junction of 
the Carboniferous Limestone with the Lower Old Red is traced towards the 
east, the thickness of strata between the two formations gradually increases, 
until at the Pentland Hills the whole of the Lower Carboniferous series and a 
considerable part of the Upper Old Red have come in ; and these strata, as at 
Lesmahagow, rest quite unconformably on the base of the Lower Old Red 
Sandstone and the higher beds of the Upper Silurian. Hence it becomes 
apparent that in the south of Scotland, as in L-eland, there is a great physical 
break between the Upper Old Red Sandstone and the lower part of that 
formation. 
The author next pointed out the character of the Upper Old Red Sandstone 
in East Lothian and Berwickshire ; showing that it graduated by imperceptible 
stages into the Lower Carboniferous sandstones, and formed with these one 
