of it as such. But he eagerly followed it up now, by
visiting every bank of the boulder-clay in his locality within twenty
miles of Thurso, and found them all charged, from top to bottom, with
comminuted shells, however great their distance from the sea, or their
elevation over it. The fragments lie thick along the course of the
Thorsa, where the encroaching stream is scooping out the clay for the
first time since its deposition, and laying bare the scratched and
furrowed pebbles. They occur, too, in the depths of solitary ravines far
amid the moors, and underlie heath, and moss, and vegetable mould, on
the exposed hill-sides. The farm-house of Dalemore, twelve miles from
Thurso as the crow flies, and rather more than thirteen miles from Wick,
occupies, as nearly as may be, the centre of the county; and yet there,
as on the sea-shore, the boulder-clay is charged with its fragments of
marine shells. Though so barren elsewhere on the east coast of Scotland,
the clay is everywhere in Caithness a shell-bearing deposit; and no
sooner had Mr. Dick determined the fact for himself, at the expense of
many a fatiguing journey, and many an hour's hard digging, than he found
that it had been ascertained long before, though, from the very
inadequate style in which it had been recorded, science had in scarce
any degree benefited by the discovery. In 1802 the late Sir John
Sinclair, distinguished for his enlightened zeal in developing the
agricultural resources of the country, and for originating its
statistics, employed a mineralogical surveyor to explore the underground
treasures of the district; and the surveyor's journal he had printed
under the title of "Minutes and Observations drawn up in the course of a
Mineralogical Survey of the County of Caithness, ann. 1802, by John
Busby, Edinburgh." Now, in this journal there are frequent references
made to the occurrence of marine shells in the blue clay. Mr. Dick has
copied for me the two following entries,--for the work itself I have
never seen:--"1802, Sept. 7th.--Surveyed down the river [Thorsa] to
Geize; found blue clay-marl, _intermixed with marine shells_ in great
abundance." "Sept. 12th.--Set off this morning for Dalemore. Bored for
shell-marl in the 'grass-park;' found it in one of the quagmires, but to
no great extent. Bored for shell-marl in the 'house-park.' Surveyed by
the side of the river, and found blue clay-marl in great plenty,
_intermixed with marine shells, such as th