PROCEEDINGS OF THE PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
33 
gorm range, Ben G-hloe, Ben Lawers, Schiehallion, and 
many other hills of less note. In addition to the hills, no 
less than fourteen lochs were visible, from the larger ones, 
such as Tay, Bannoch, and Tumrnel, down to the smaller 
hill lochans. 
Farragon attains an altitude of 2559 feet above sea- 
level, and being so high, it was with much interest that it 
was observed that the ice-sbeet of the Great Ice Age 
had overflowed the hill, and left its mark thereon in the 
form of many “roches moutonnites ,” which, to the observers 
standing on the hill, afforded a striking illustration of the 
immensity of the ice-sheet of that age. Looking at the 
green and heather-covered hill-sides, it was difficult to 
imagine that they had at no very distant period (compara¬ 
tively with their age) been buried deep under a continuous 
mass of ice, not lying quietly on them, but moving con¬ 
tinually in one direction, and by its weight and irresistible 
pressure hewing out the hills in forms which they retain 
to the present day. 
But time was speeding, and trains, like wind and tide, 
do not wait, so a move was made for Aberfeldy, which 
was reached in due time. 
September 24th. 
4. To the Dens of Kilspindie, Balmyre, and Pitroddie. 
The excursion was conducted by the President of the 
Society, Dr Geikie. The day to begin with, though dull, 
was not unfavourable, and much enjoyable work was 
done; but the after part proved wet, and interfered 
materially with the pleasure of the excursionists. 
While passing along the foot of Kinnoull Hill, Dr 
Geikie took occasion to point out the general geological 
structure of the ground. The lofty cliffs are built up of 
a series of ancient lava-flows, sometimes separated by thin 
bands of conglomerate, aDd resting upon a much thicker 
bed of the same kind of rock. This lower conglomerate 
is well seen in the neighbourhood of Kinfauns Castle. 
Underneath it again comes another series of ancient lava- 
flows, which are well exposed in Moncreiffe Hill, and the 
hills behind Inchyra. Thus, in passing from Perth down 
the Tay to Inchyra, we descend from the top to the 
bottom of the ancient igneous rocks of the Sidlaw range,— 
the inclination of the beds, being persistently towards 
north-west. The Tay, in short, has cut its course across 
a volcanic ridge of Lower Old Bed Sandstone age. 
Dr Geikie also pointed out the evidences of glacial work 
in the general features of the ground,—the rocky northern 
slopes of Moncreiffe Hill being well smoothed and abraded 
by the ice which came down the Tay valley, and over¬ 
flowed all the district in a prevalent south - easterly 
direction : and he indicated the places where glacial striae 
and boulder - clay might be seen. The well-marked 
terraces of sand, gravel, clay, and silt which form so con¬ 
spicuous a feature in the landscape, weref also commented 
upon. The highest of these is very fragmentary, but is 
well developed between Lower Craigie and Priarton. 
This terrace car-ries one back to the closing scenes of the 
Ice Age, and tells of a time when the sea-level stood 100 
feet higher than now;—so that the tide then flowed for 
many miles up into Strathmore. Glaciers then existed in 
the Highland glens, and much floating ice came down the 
ancient estuary of the Tay, scattering erratics and debris 
as it journied towards the open sea. The most con¬ 
spicuous terrace, however, is that which is traversed by 
the main road from Perth to Dundee. The average level 
of this terrace is some 45 feet or so above mean tide. It 
is composed chiefly of silt and clay, and is evidently of 
estuarine and marine origin,—sea-shells having been found 
in it at various places, even as far up as Perth, where 
oysters were obtained recently during some excavations in 
the clay at the General Prison. This old terrace is of 
post-glacial age, and overlies the well - known buried 
“ forest-bed.” This latter is best exposed along the banks 
of the Earn, above and below Bridge of Earn, but it also 
crops out from underneath the clay at the Priarton. It 
has yielded remains of oak and Scots fir, together with 
many reed-like plants and numerous seeds and wing-cases 
of beetles. Most of the remains of trees seem to have 
been drifted, but in some places they appear to occupy 
the place of growth. An ancient canoe, hollowed out of 
a single trunk of Scots fir, was discovered at the Priarton 
resting on the “ forest-bed.” It had been buried under 
the whole thickness of the Carse-clay. We had evidence, 
therefore, to show that after the sea had disappeared from 
the neighbourhood of Perth in late glacial times, our 
climate became mild and genial, and a thick forest-growth 
overspread the land. At that time the land seems to 
have extended further seawards than at present. - But the 
presence of the Carse-clays, which overlie the forest-bed, 
shows us that the sea again gained upon the land, and the 
tide again flowed far above Perth,—the sea-level then 
attaining a height of 45 to 50 feet. While these conditions 
obtained the climate would appear to have become de- 
