ts
varied structure and appearances, our planet must have passed. In the
survey of such a field two things are specially worthy to be taken
into account--the widening of the intellectual horizon and the
reaction of expanding knowledge upon the intellectual organ itself.

At first, as in the case of ancient glaciers, through sheer want of
capacity, the mind refuses to take in revealed facts. But by degrees
the steady contemplation of these facts so strengthens and expands the
intellectual powers, that where truth once could not find an entrance
it eventually finds a home. [Footnote: The formation, connection,
successive subsidence, and final disappearance of the glacial lakes of
Lochaber were illustrated in the discourse here reported by the model
just described, constructed under the supervision of my assistant, Mr.
John Cottrell. Glen Gluoy with its lake and road and the cataract
over its col; Glen Roy and its three roads with their respective
cataracts at the head of Glen Spey, Glen Glaster, and Glen Spean, were
all represented. The successive shiftings of the barriers, which were
formed of plate glass, brought each successive lake and its
corresponding road into view, while the entire removal of the barriers
caused the streams to flow down the glens of the model as they flow
down the real glens of to-day.]

A map of the district, with the parallel roads shown in red, is
annexed.

LITERATURE OF THE SUBJECT.

THOMAS PENNANT.--A Tour in Scotland. Vol. iii. 1776, p. 394. JOHN
MACCULLOCH.--On the Parallel Roads of Glen Roy. Geol. Soc. Trans.
vol. iv. 1817, p. 314.

THOMAS LAUDER DICK (afterwards SIR THOMAS DICK-LAUDER, Bart.)--On the
Parallel Roads of Lochaber. Edin. Roy. Soc. Trans. 1818, vol. ix.
p. 1.

CHARLES DARWIN.--Observations on the Parallel Roads of Glen Roy, and
of the other parts of Lochaber in Scotland, with an attempt to prove
that they are of marine origin. Phil. Trans. 1839, vol. cxxix. p. 39.

SIR CHARLES LYELL.--Elements of Geology. Second edition, 1841.

Louis AGASSIZ.--The Glacial Theory and its Recent Progress--Parallel
Terraces. Edin. New Phil. Journal, 1842, vol. xxxiii. p. 236.

DAVID MILNE (afterwards DAVID MILNE-HOME).--On the Parallel Roads of
Lochaber; with Remarks on the Change of Relative Levels of Sea and
Land in Scotland, and on the Detrital Deposits in that Country. Edin.
Roy. Soc. Trans. 1847, vol. xvi. p. 395.

ROBERT CHAMBERS.--Ancient Sea Margins. Edinburgh, 1848.