d south on the eastern side, and have a gentler
trend westward from the head.

The configuration of the coasts is perhaps the chief cause of the
peculiarities of tides in the Channel. From the entrance as far as
Portland Bill the time of high water is found to be progressively later
in passing from west to east, being influenced by the oceanic tidal
stream from the west under conditions which are on the whole normal. But
eastward of a line between Portland Bill and the Gulf of St Malo these
conditions are changed and great irregularities are observed. On the
English coast between Portland Bill and Selsey a double tide is found.
At Portland this double tide corresponds approximately with the time of
low water in the regular tidal progression, and the result is the
occurrence of two periods of low water, separated by a slight rise known
locally as "gulder." But farther east the double tide corresponds more
nearly with the time of high water, and in consequence either the effect
is produced of a prolonged period of high water, or there are actually
two periods of high water, as at Southampton. Various causes apparently
contribute to this phenomenon. The configuration of the coast line is
such as to present at intervals barriers to the regular movement of the
tidal wave (west to east), so that reflex waves (east to west) are set
up. In the extreme case at Southampton the tidal effect is carried from
the outer Channel first by way of the Solent, the strait west of the
Isle of Wight, and later by way of Spithead, the eastern strait. Finally
the effect of the tidal stream entering the Channel through the Strait
of Dover from the North Sea must be considered. The set of this stream
towards the Strait of Dover from the east corresponds in time with that
of the Channel stream (i.e. the stream within an area defined by Start
Point, the Casquets, Beachy Head and the mouth of the Somme) towards the
strait from the west; the set of the two streams away from the strait
also corresponds, and consequently they alternately meet and separate.
The area in which the meeting and separation take place lies between
Beachy Head and the North Foreland, the mouth of the Somme and Dunkirk.
Within this area, therefore, a stream is formed, known as the
intermediate stream, which, running at first with the Channel stream and
then with the North Sea stream, changes its direction throughout its
length almost simultaneously, and is never slack. Under the