170 
SKCIJKTAHY's HEPOllT. 
mouths at a period when they were not filled with local glaciers. 
In considering the Forth ice, the overflow at Heriot proves that 
the Tweed ice dwindled before the Forth ice, and this is con- 
firmed by the overflow valleys and other -glacial phenomena of 
the eastern Lammermuirs. Other evidence combines to prove 
that there was a progressive dwindling of the British glaciers 
from south to north at the close of the Glacial Period, and prob- 
ably the Scandinavian ice-sheet diminished in the same direction, 
thus giving a fall in the ice-surface to the south. This explains 
the fact that the overflow valleys are found plentifully on the 
south slopes of tlie principal east and west valleys, but very seldom 
on their northern sides, the free drainage being southwards 
into a great Xorth Sea lake, and outwards, in all probability, 
by the Straits of Dover, which would be a great glacial over- 
flow. 
During the excursion Fans was visited and two large masses 
of olivine dolerite in the neighbourhood examined. These showed 
beautiful columnar structure, as also did a boss of dolerite near 
Dryburgh. A visit was paid to Duns to examine the granite of 
Cockburn Law. The edges of the mass were only seen in situ 
showing a fine-grained bluish-grey granite, with occasional 
pinkish patches. Boulders, which were very plentiful, gave a 
coarser rock very rich in biotite, and forming a basic granite 
or granitite. 
This excursion also revealed a very interesting river diver- 
sion, the Whiteadder crossing the igneous mass in a deep gorge, 
whicli must have been due to interrupted eastward drainage by 
ice. 
The Black Hill of Earlston was ascended and the sanidine 
trachyte examined. In a quarry on the flank of the hill the 
igneous rock was seen overlying the Old Red in a beautiful 
section, and contact specimens were obtained. Tlie igneous 
rock was beautiful, variegated along joint planes by infiltration 
dendritic markings. At Bremerside. near Dryburgh. a mass of 
platy trachyte was examined, which was probably part of the 
same sheet as the Black Hill. A visit was paid to the Eildon 
