68 Prof. OC. Lapworth—Ballantrae Rocks of South Scotland. 
until this work has been accomplished, and the Scottish Arenig, 
Wenlock and Ludlow strata studied in equal detail, can we claim 
that our knowledge of the geological structure of the Scottish Uplands 
is even fairly complete. 
But, if the ideas expressed in this paper are well founded, the 
main results of future investigations, in so far as they affect the 
general mapping of the Upland area proper, can even now be 
sketched in outline. The Axial or Ardwell Group of the earlier 
investigators will disappear as a separate series, and will take its | 
place as the southerly extension of the Gala or Queensberry Group 
to the north. The Dalveen (and Haggis Rock) (Lugate Series) ; the 
Lowther Group (Heriot), and the Leadhills Black Shale and Caradoc 
and Carsphairn Group (Moorfoot Series) will all be found to be 
regional geological complexes of a thickness far inferior to that with 
which they have hitherto been credited: but, nevertheless, each 
possessing a high local value, as significant of the local peculiarities 
and intermediate lithological condition of the Moffat Terrane in the 
central districts. These three “central” groups, when worked out 
in detail and restricted to their natural components, will be found to 
follow each other in the order given above :—the Dalveen-Lugate 
Group answering to the Birkhill Shales, the Lowther-Heriot 
Group to the Hartfell (Upper, etc.), while the strata of the Lead- 
hills-Moorfoot Group must be re-arranged, and will fall, part into 
the Lower Hartfell (Caradoc), and part into the Glenkiln (Upper 
Llandeilo) formations. 
The general geological map of the Uplands will show that the 
rocky floor of that region is composed of strata ranging almost from 
the base of the Ordovician up to the summit of the Silurian. The 
outcrop of the main boundary-line between the strata of the two 
systems (which is on or about the horizon of the so-called Haggis 
Rock) will be found to pass obliquely across the region from the north- 
east margin of the Uplands near Dunbar, over the crest of the Lam- 
mermuirs, to the south of the Moorfoots, and north of the town of 
Peebles, over the valley of the Tweed near Neidpath and the Crock, 
into the valley of the Clyde near Elvanfoot ; and thrown next to the 
southward by the anticlinal of the upper reaches of the Shinnel, 
will be found to cross the southern part of the granitic range of the 
Kells towards the sea-coast south of Portpatrick. To the north and 
north-east of this guiding line the mass of the strata will be proved 
to be Ordovician; such Silurian rocks as occur forming outliers 
parallel with the great boundary fault. To the south-east of the 
divisional line the mass of the strata must be classed as Silurian; 
the Ordovician rocks only occurring locally as long lenticular inliers, 
gradually diminishing in systematic importance as they are followed 
across the country from north to south, and from west to east. 
Of the Upland “formations,” the Arenig appears to have the 
smallest superficial extent, its outcrops being as yet confined to the 
Ballantrae region (unless indeed some of the so-called Old Red Sand- 
stone near the boundary-line is of this age): the true Caradoe will 
be mapped as narrow boat-like sheets along the greater anticlinal 
