Mr. David Milne (afterwards Milne-Home) (517/8. "Trans. R. Soc. Edinb."
Volume XVI., page 395, 1847.) in 1847 upheld the view that the ledges
represent the shore-lines of lakes which were imprisoned in the valleys by
dams of detrital material left in the glens during a submergence of 3,000
feet, at the close of the Glacial period. Chambers, in his "Ancient Sea
Margins" (1848), expressed himself in agreement with Mr. Darwin's marine
theory. The Agassiz-Buckland theory was supported by Mr. Jamieson (517/9.
"Quart. Journ. Geol. Soc." Volume XIX., page 235, 1863.), who brought
forward additional evidence in favour of the glacial barriers. Sir Charles
Lyell at first (517/10. "Elements of Geology," Edition II., 1841.)
accepted the explanation given by Mr. Darwin, but afterwards (517/11.
"Antiquity of Man," 1863, pages 252 et seq.) came to the conclusion that
the terrace-lines represent the beaches of glacial lakes. In a paper
published in 1878 (517/12. "Phil. Trans. R. Soc." 1879, page 663.), Prof.
Prestwich stated his acceptance of the lake theory of MacCulloch and Sir T.
Lauder Dick and of the glacial theory of Agassiz, but differed from these
authors in respect of the age of the lakes and the manner of formation of
the roads.

The view that has now gained general acceptance is that the parallel roads
of Glen Roy represent the shores of a lake "that came into being with the
growth of the glaciers and vanished as these melted away." (517/13. Sir
Archibald Geikie, loc. cit., page 269.)

Mr. Darwin became a convert to the glacier theory after the publication of
Mr. Jamieson's paper. He speaks of his own paper as "a great failure"; he
argued in favour of sea action as the cause of the terraces "because no
other explanation was possible under our then state of knowledge."
Convinced of his mistake, Darwin looked upon his error as "a good lesson