296 
VOLCANOES OF THE LOWER OLD RED SANDSTONE book v 
lilies of the great faults, though they lie uiiconfonnably on the rocks beneath, 
are not the basement portions of the Oltl Keel Sandstone. On the contrary, 
where their probable stratigrapliical horizons can be recognized or inferred, 
they are found to belong to parts of the series considerably above the base 
of the whole. They point to the gradual sinking of the basin and the 
creeping of the waters with their littoral shingles further and further up 
the slopes of the hills on either side (Fig. 7?>). 
Kut this is not all the evidence that can be adduced to show that the 
limits of the lake extended considerably beyond the lines of dislocation 
between which the present area of Old Eed Sandstone mainly lies. No 
one can look at the noble escarpments of the Braes of Donne on the one 
Fio. 74. — Craig Beinn iiau-Eim (20e7 feet), east of Uam Var, Braes of Doiuie. Old Red Conglomerate, 
with the truncated emls of the strata looking across into the Highlands ; moraines of Corry Beach 
in the foreground. 
side (Fig. 74), or walk over the upturned conglomerates and andesites which 
dank the I.anarkshire uplands on the other, without being convinced that if 
the elfects of the boumlary faults could be undone, so as to restore the original 
structure of the ground, the prolongations of the rocks, now removed by 
denudation, would be found sweeping far into the Highlands on the north 
and into the Silurian Uplands on the south. 
If the area of “ Lake Caledonia ” were taken to be defined by the boundary 
faults, it covered a space of about 10,000 square miles. But, as we know 
that it certainly stretched beyond the limits marked by these faults, it 
must have been of still greater extent. We shall probably not exaggerate 
if we regard it as somewhat larger than the present Lake Erie, the superficies 
of wdiich is about 9900 square miles. In this long narrow basin the 
