Geoscience Reference
In-Depth Information
Figure 6.4 Junction of granite
and schist at Glen Tilt, Scotland.
(a) Granite; (b) Limestone;
(c) Schist. Here Hutton found
older rocks cross-cut by veins
of granite, which proved it was
a plutonic rock (from C. Lyell,
Manual of ElementaryGeology
(1855), p. 572).
into the glen. Undeterred, they leapt over a dyke and ran down the
valley. The Duke tried to assert his right to keep trespassers off his
estates, but the 'Battle of Glen Tilt' became widely advertised in song
and in print, and the whole affair ended up in court when an Aberdeen
solicitor by the name of Abraham Torrie, together with two others,
took up the case on behalf of the ramblers. It was declared that a right
of way did exist and that 'the pursuers and all others were entitled to
the free and uninterrupted use of it'. This action remains one of the
most celebrated of Scottish lawsuits.
In 1786 Hutton found similar cross-cutting relationships in gran-
ites near Galloway. The following year sawHutton on the Isle of Arran
with John Clerk's son John (1757-1832) (later Lord Eldin) where at
Sannex, at Goatfell and in Glenrosa he observed granite veins in the
surrounding rocks, andmore importantly, at its northern end, he discov-
ered an unconformity. He did not actually call it an unconformity - this
term was first used by the Wernerian Robert Jameson in 1805. Hutton
later described the feature in his 1795 treatise (volume I, page 429-430):
I had long looked for the immediate junction of the secondary or
low country strata with the alpine schistus ...; the first place in
which I observed it was ... at the mount of Lough Ranza. Here the
schistus and the sandstone strata both rise inclined at an angle of
