geological talks, and the pleasure of seeing Mrs. Horner and yourself here.
(518/3. This letter is published in the privately printed "Memoir of
Leonard Horner," II., page 103.)

[Here follows Darwin's Memorandum.]

The Parallel Roads of Glen Roy, in Scotland, have been the object of
repeated examination, but they have never hitherto been levelled with
sufficient accuracy. Sir T. Lauder Dick (518/4. "On the Parallel Roads of
Lochaber" (with map and plates), by Sir Thomas Lauder Dick, "Trans. R. Soc.
Edinb." Volume IX., page 1, 1823.) procured the assistance of an engineer
for this purpose, but owing to the want of a true ground-plan it was
impossible to ascertain their exact curvature, which, as far as could be
estimated, appeared equal to that of the surface of the sea. Considering
how very rarely the sea has left narrow and well-defined marks of its
action at any considerable height on the land, and more especially
considering the remarkable observations by M. Bravais (518/5. "On the
Lines of Ancient Level of the Sea in Finmark," by M. A. Bravais, translated
from "Voyages de la Commission Scientifique du Nord, etc."; "Quart. Journ.
Geol. Soc." Volume I., page 534, 1845.) on the ancient sea-beaches of
Scandinavia, showing the they are not strictly parallel to each other, and
that the movement has been greater nearer the mountains than on the coast,
it appears highly desirable that the roads of Glen Roy should be examined
with the utmost care during the execution of the Ordnance Survey of
Scotland. The best instruments and the most accurate measurements being
necessary for this end almost precludes the hope of its being ever
undertaken by private individuals; but by the means at the disposal of the
Ordnance, measurements would be easily made even more accurate than those
of M. Bravais. It would be desirable to take two lines of the greatest
possible length in the district, and at nearly right angles to each other,