246 
THE TERTIARY VOLCANOES 
BOOK VIII 
have been supposed to have effectually destroyed all evidence of the con- 
tinuation of the rock in a westerly direction. Some years ago, however, my 
friend Prof. Heddle, while cruising among the Inner Hebrides, landed upon 
the little uninhabitated islet of Hysgeir, which, some eighteen miles to the 
westward of Eigg, rises out of the open sea. He at once recognized the 
identity of the rock composing this islet with that of the Scuir, and in the 
year 1892 published a brief account of this interesting discovery. 1 
I have myself been able to land on Hysgeir in two successive summers, 
and can entirely confirm Prof. Heddlc’s identification. The islet stands on 
the eastern edge of the submarine ridge which, running in a north-easterly 
direction, culminates in the island of Canna. Hysgeir is a mere reef or 
skerry, of which the top rises only 38 feet above the Ordnance datum-level. 
Its surface is one of bare rock, save where a short but luxuriant growth of 
grasses has found root on the higher parts of two or three of its ridges, and 
on the old storm-beach of shingle which remains on the summit. The rock 
undulates in long low swells, that run in a general direction 20° to 45 3 west 
of north, and are separated by narrow channels or hollows. The place is a 
favourite haunt of gulls, terns, eider-ducks and grey seals, and is used by the 
proprietor of Canna for the occasional pasturage of sheep or cattle. So 
numerous are the sea-fowl during the breeding-season that the geologist, 
intent upon his own pursuits, may often tread on their nests unawares, while 
he is the centre of a restless circle of white wings and anxious cries. 
The pitchstone of Hysgeir, like that of Eigg, is columnar, the columns 
being irregularly polygonal and varying from three to ten inches in diameter. 
They are packed so close together that the domes of rock on which their 
ends appear look like rounded masses of honeycomb. They may here and 
there be observed to be arranged radially with their ends at right angles to 
the curved exterior of the ridges, as if this external surface represented the 
original form of the cooled pitchstone, and were not due to mere denudation. 
There can be no doubt, however, that the island has been well ice-worn. 
At the north-west promontory a beautiful example of. fan-shaped 
grouping of columns may be observed on a face of rock which descends 
vertically into the sea. Here, too, is almost the only section on which the 
sides of the columns may be examined, for, as a rule, it is merely their ends 
on the rounded domes which are to be observed, and which everywhere slip 
under the waves. The columns in a cliff from 15 to 20 feet high show the 
slightly wavy, starch-like arrangement so often to be met with among the 
plateau- basalts. 
The rock presents a tolerably uniform texture throughout, though in 
some parts it is blacker, more resinous, and less charged with porphyritic 
enclosures than in the general body of the rock. Large fresh felspars are 
generally scattered through it. To the naked eye it reproduces every 
feature of the pitchstone of the Scuir of Eigg. 
A microscopic examination completes our recognition of the identity of 
1 Appendix C to A Vertebrate Fauna of Argyle and the Inner Hebrides, by Messrs. .1. A. 
Harvie-Brown and Thomas E. Buckley, p. 248. 
