21 
PROCEEDINGS OF THE PERTHSHIRE SOCIETY OP NATURAL SCIENCE. 
\ 
Overlying the till come the great sand and gravel- 
series — the kames and mounds — which are so well- 
developed, especially in Strathmore between Lindertis 
and Glamis, and again near Monzie, and Ochtertyre, 
and elsewhere. Contemporaneous with these are the 
great flats of sand, gravel, and clay of Strathmore and 
other regions in the low grounds. All these deposits 
were laid down during the melting of the great ice-sheet. 
They correspond to the gravelly moraines and torrential 
deposits of Switzerland and North Italy, and betoken a 
time when glaciers occupied the Highland glens, and great 
summer-floods deluged the low grounds. 
More recent than these are the mounds and hummocks 
of earthy debris, coarse gravel, and angular blocks which 
occur in the Highland glens themselves. These last are 
the terminal moraines laid down by the glaciers as they 
slowly retired up their valleys, and finally melted 
away. Associated with these moraines we generally find 
high-level flats and terraces of gravel, which are evidently 
the work of the rivers when these lowed in larger 
volume, and were subject to greater floods, than now- 
a-days. I may mention that during the retreat of 
the glaciers the sea gained upon the land, and reached 
to a height of at least 100 feet above its present level. To 
this period belong the clays with Arctic shells at Errol, 
the brick-clays worked at Pitfour, and the higher terraces 
of gravel, sand, and clay that fringe the slopes of the 
valleys of the Tay and Earn in our own neighbourhood. 
The recent deposits are typically represented by the 
buried peat-bed and carse-clays of the Earn and the Tay. 
The peat-bed (seen at the Eriarton, and particularly well 
exposed along the banks of the Earn for several miles 
above its junction with the Tay) represents a time when 
the sea had again retired, and when the land probably 
extended further seawards than it now does. Much of the 
peaty matter is made up of drifted fragments of trees, 
especially fir and hazel. Now and again, however, we see 
rootlets penetrating the old soil, so that we may infer that 
the peat represents a former land surface liable to be 
flooded by the swollen rivers. 
The overlying carse-clay is evidently an estuarine de¬ 
posit, accumulated at a time when the sea-level stood 
some 45 feet or so higher than at present. It is in¬ 
teresting to note that the earliest relic of man in Perth¬ 
shire— a “dug-out” canoe — was discovered underneath 
the brick-clay at the Eriarton. Possibly other human 
relics may yet be discovered on the same horizon; and 
it might be well if some of our local observers would, 
after heavy floods, take the opportunity of examining the 
old peat-bed on the banks of the Earn. It is quite 
possible that they might be rewarded with other and not 
less interesting relics belonging to the earlier stage of what 
is termed the Neolithic Period. The occurrence of the 
canoe at the Friarton shows us that man was in occupation 
of this district at a time anterior to the formation of the 
carse-clays. He was here before the sea had risen to the 
45-feet level, and no doubt paddled his canoe in water 
which covered the present site of Perth to a height of 30 
feet, and when the tide flowed up to and beyond Stanley. 
The latest deposits pertaining to the Recent period are 
the lower alluvial flats which border the present lakes, 
streams, and rivers,—and the peat-bogs. , In these we read 
the history of the gradual changes which ushered in the 
present—a history which, I may say, is as yet only very 
partially worked out. 
I have now sketched in very meagre outline the 
general geology of the county, in the hope that those 
members of the Society who are interested in the 
stony science may fill in the details as opportunity oc¬ 
curs. There is certainly no wide and abundant harvest 
for the palaeontologist to cultivate in Perthshire. The 
strata., are as a rule barren of fossils, but there is sufficient 
inducement to the hammer-bearing student to keep his 
eyes open, for it is quite possible that some happy dis¬ 
covery of fossil organic remains may await him. As I 
have said, no fossils have yet been recorded from the 
Silurian strata, while only a few ill-preserved specimens 
of plants and some fish and crustaceans have been obtained 
from the Old Red Sandstone. The Carboniferous strata 
are represented only in the small detached part of Perth¬ 
shire on the borders of the Eirth of Forth, and these rocks 
are doubtless more fossiliferous than those belonging to any 
of the other formations in the county. Near Bridge of 
Earn, in some dark shales which possibly belong to the 
very top of the Upper Old Red Sandstone or the base of 
the carboniferous, plants and shells are not uncommon. 
The clays of Errol are well known to geologists as contain¬ 
ing a number of shells of Arctic character, and the fluvio- 
glacial deposits of the Carse might be searched more 
assiduously than they have yet been, in the hope of dis¬ 
covering more relics of the old marine fauna of the Ice 
Age. But, as will be readily understood, it is the student 
of physical geology who will find most ample scope for 
observation in Perthshire. He could desire no better 
region in which t® begin his investigations, and we may 
look forward to the time when the opportunities afforded 
by this Society may induce an increasing number of the 
young to engage in this most fascinating branch of Natural 
History study. 
