westerly wind, about eight o'clock in the morning the whole Firth, from
Dunnet Head to Hoy Head in Orkney, seems as smooth as a sheet of glass.
About nine the sea begins to rage for about one hundred yards off the
Head, while all without continues smooth as before. This appearance
gradually advances towards the Firth, and along the shore to the east,
though the effects are not much felt along the shore till it reaches
Scarfskerry Head, as the land between these points forms a considerable
bay. By two o'clock the whole of the Firth seems to rage. About three in
the afternoon it is low water on the shore, when all the former
phenomena are reversed, the smooth water beginning to appear next the
land and advancing gradually till it reaches the middle of the Firth. To
strangers the navigation is very dangerous, especially if they approach
near to land. But the natives along the coast are so well acquainted
with the direction of the tides, that they can take advantage of every
one of these currents to carry them safe from one harbour to another.
Hence very few accidents happen, except from want of skill or knowledge
of the tides."

[Illustration: A NORTH SEA ROLLER.]

There were some rather amusing stories about the detention of ships in
the Firth. A Newcastle shipowner had despatched two ships from that port
by the same tide, one to Bombay by the open sea, and the other, via the
Pentland Firth, to Liverpool, and the Bombay vessel arrived at her
destination first. Many vessels trying to force a passage through the
Firth have been known to drift idly about hither and thither for months
before they could get out again, and some ships that once entered
Stromness Bay on New Year's Day were found there, resting from their
labours on the fifteenth day of April following, "after wandering about
like the _Flying Dutchman_." Sir Walter Scott said this was formerly a