356 PROFESSOR GEIKIE ON THE 
very roots of the mountains. The line of the Great Glen was even then marked 
by a long straight valley in which the lake stretched far to the south-west, if 
indeed there was not a communication, more or less interrupted, between this 
northern basin and the Lake of Lorne. The mountainous country of Ross 
and Sutherland formed a bold border-land on the west side. But the coast- 
line appears to have turned westwards across the north-eastern part of Suther- 
landshire, at least as far as the base of the noble granite peaks of Ben Laoghall 
and the Kyle of Tongue. Towards the north, Lake Orcadie stretched over 
the site of Caithness and the whole of the Orkney Islands, but save one or two 
fragments of its ancient islets, no trace of its shores is to be seen until we reach 
the southern end of the Shetland group, and meet there with some of its lit- 
toral conglomerates. | 
On the west coast of Norway, about the mouths of the Sognefjord and 
Dalsfjord, and on the neighbouring islands, huge cliffs of a massive con- 
glomerate occur, the resemblance of which to those of the north of Scotland 
was pointed out many years ago by NauMANN.* Red conglomerates and sand- 
stones likewise occur round Christiana, which have been referred to the Old 
Red Sandstone.. Of course these identifications in the absence of fossil — 
evidence must be regarded as only provisional ; and even if they are eventually 
sustained, they would not prove that Lake Orcadie extended continuously 
across what is now the trough of the North Sea to the margin of the Scandi- 
navian highlands. At the same time this former north-easterly prolongation 
of the basin seems to me extremely probable. The occurrence of a few species 
of fishes common to the Old Red Sandstone of the north of Scotland and of 
Russia goes far to show a connection, more or less restricted, no doubt, 
between these distant areas, or at least suffices to indicate that any watershed 
which separated them was not a wholly insuperable barrier to their respective 
faunas. . a 
Even if we restrict the area of Lake Orcadie merely to the space over 
which its deposits can be traced within the Scottish islands, the basin will be 
found to have had no inconsiderable dimensions. Like the majority of the 
larger features of the country, it probably had a north-easterly trend. From its 
southern margin at Loch Ness to its northern limit in Shetland is a distance of 
250 miles. Were we to include the Norwegian conglomerates of the Bergen- 
-huus as marking the shore-line in that direction, the length of the basin would 
be increased to somewhere about 400 miles. Of its breadth little can be said 
from the fragmentary portions which alone remain ; but a line drawn from the 
Kyle of Tongue to Aberdour in Aberdeenshire, would give a breadth of about 
120 miles. I shall have occasion to show, however, that there is good reason 
* “ Beitrige zur Kenntniss Norwegens,” vol. ii. p. 118, e¢ seq. 

