HH62/1/INVERN/7

Transcription

[page] 6

priori reasoning. Each separate set of facts requires separate
investigation, and the results of one enquiry may not be assumed
in the presecution of another. In the present report few con-
clusions have been drawn; it is essentially a collection of statistics
which may be of use in the future.

GEOLOGICAL FEATURES OF THE COUNTY OF INVERNESS.
The relationship between geological formation and disease is
well known. The broad geological features of the County are
as follow:-

OUTER HEBRIDES.
Beginning with the Outer Hebrides, extending from Harris
to Barra Head, they are composed of crystalline gneiss and schist,
traversed by occasional dykes of basalt. In the valleys and low-
lying ground adjoining the sea, there is a thin covering of boulder
clay.

THE ISLAND OF SKYE.
This island is mainly composed of teriary volcanic rocks.
That portion of the island lying to the north of the Coolin Hills
and Loch-Sligachan is almost wholly covered by a great succession
of lava floors, in nearly horizontal sheets, resting on different
members of the secondary stratified rocks. Here and there round
the coast the latter sedimentary strata are exposed where the
overlying volcanic rocks have been worn away. These sedimentary
strata, including the lias, lower oolite, and Oxford clay, are exposed
in Loch-Bay, Uig Bay, at Duntulm, and along a large part of the
east coast, from Loch-Staffin to Loch Sligachan. Similar sedi-
mentary strata are met with between Broadford Bay and Loch-
Slapin. The Coolin Hills are composed of basic eruptive rocks,
while to the east of the Coolin Hills, between Loch-Sligachan and
Broadford, the mountains consist of granitoid rocks of acid
composition.
In the peninsula of Sleat there is a limited development of
the Torridon sandstone, and the overlying quartzites and lime-
stones which are the southern continuations of the ancient
sedimentary formations in the west of Sutherland and Ross.
Along the eastern portion of the peninsula the crystalline schists
are met with.

RAASAY AND RONA.
The Island of Rona and the northern part of Raasay south
to a point near Brochal Castle is composed of crystalline gneiss,
while the central portion of Raasay is occupied by stratified beds
(sandstone and flags) of the age of the Torridon sandstone. The
southern portion of the island presents a fine development of the
secondary stratified rocks ranging from the lias clay to the oolite
formation. There are small patches of the volcanic rocks of Skye
in the southern portion of the island.

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EIGG.
This island is mainly composed of inter-bedded volcanic rocks
similar to those in the northern part of Skye, but round the
northern part of the coast the Oxford clay is met with.

RUM.
In the northern part of this island there is a fine development
of the Torridon sandstone, while the remainder is occupied by acid
and basic igneous rocks, similar to the rocks in the Coolin Hills
and south of Sligachan.

THE MAINLAND.
The mainland portion of the County is composed of different
types of crystalline gneiss and schist, on which rest unconformably
the respresentatives of the Old Red Sandstone. The latter are
sparingly developed: they form a continuous belt from Culloden
Moor to the Falls of Foyers, while to the west of Fort-Augustus
they occupy a narrow strip of ground along the east shore of
Loch-Oich. On the north-west side of the Great Glen they ex-
tend from Clachnaharry to near the mouth of Loch-Ness. They
reappear at the mouth of Glen-Urquhart and cap Mealfourvonie,
There is also an important development of the old Red con-
glomerates and sandstones in Beauly basin.
Excepting these areas, the remainder of the County is occu-
pied by crystalline gneiss and schist pierced by large masses of
intrustive igneous rocks. Of the latter, the most important areas
lie along the north-west shore of Loch Ness at Abriachan, and
again to the south of the Old Red Sandstone area between Farraline
and Foyers. In the valleys there is a considerable development
of glacial deposits, boulder clay, and moraines; while round the
shores of the Beauly Firth there are remains of the raised
beaches, consisting of stratified gravels, sand, and clay.
I have been enabled to give these geological notes through
the courtesy of Mr Horne, of the Geological Survey of Scotland.

AREA AND POPULATION.

AREA.
[table inserted]

These figures are according to Ordnance Survey. Alterations
have recently been made by the Boundary Commission, which
have increased the acreage of the County.