The Pentland Firth lies between the north of Scotland and the Orkney
Islands, varies from five and a half to eight miles in breadth, and is
by repute the most dangerous passage in the British Isles. We were told
in one of the books that if we wanted to witness a regular "passage of
arms" between two mighty seas, the Atlantic at Dunnet Head on the west,
and the North Sea at Duncansbay Head on the east, we must cross Pentland
Firth and be tossed upon its tides before we should be able to imagine
what might be termed their ferocity. "The rush of two mighty oceans,
struggling to sweep this world of waters through a narrow sound, and
dashing their waves in bootless fury against the rocky barriers which
headland and islet present; the endless contest of conflicting tides
hurried forward and repelled, meeting, and mingling--their troubled
surface boiling and spouting--and, even in a summer calm, in an eternal
state of agitation"; and then fancy the calm changing to a storm: "the
wind at west; the whole volume of the Atlantic rolling its wild mass of
waters on, in one sweeping flood, to dash and burst upon the black and
riven promontory of the Dunnet Head, until the mountain wave, shattered
into spray, flies over the summit of a precipice, 400 feet above the
base it broke upon." But this was precisely what we did not want to see,
so we turned to the famous _Statistical Account_, which also described
the difficulty of navigating the Firth for sailing vessels. This
informed us that "the current in the Pentland Firth is exceedingly
strong during the spring tides, so that no vessel can stem it. The
flood-tide runs from west to east at the rate of ten miles an hour, with
new and full moon. It is then high water at Scarfskerry (about three
miles away from Dunnet Head) at nine o'clock. Immediately, as the water
begins to fall on the shore, the current turns to the west; but the
strength of the flood is so great in the middle of the Firth that it
continues to run east till about twelve. With a gentle breeze of