tral axis runs approximately from south-west
to north-east. The Baltic is connected with North Sea by the winding
channel between the south of Scandinavia and the Cimbrian peninsula. This
channel is usually included in the Baltic. The part of it west of a line
joining the Skaw with Christiania fjord receives the name of Skagerrak; the
part east of this line is called the Kattegat. At its southern end the
Kattegat is blocked by the Danish islands, and it communicates with the
Baltic proper by narrow channels called the Sound, the Great Belt and the
Little Belt. The real physical boundary between the North Sea and the
Baltic is formed by the plateau on which the islands Zealand, Funen and
Laaland are situated, and its prolongation from the islands Falster and
Moen to the coasts of Mecklenburg and Ruegen.

East of this plateau the Baltic proper forms a series of hollows or
troughs. The first, or Bornholm deep, lies east of the island of Bornholm,
and is separated from the next, or Gotland deep, by the Middelbank. Beyond
the Middelbank the Danziger Tiefe, an isolated depression, lies to the
south-east, while to the northeast the Gotland basin, the largest and
deepest of all, extends north-eastwards to the Gulf of Finland. Along the
Swedish coast a deep channel runs northward from outside the island of
Oland; this is entirely cut off to the south and east by a bank which
sweeps eastward and northward from near Karlskrona, and on which the island
of Gotland stands, but it communicates at its northern end with the Gotland
deep, and near the junction opposite Landsort is the deepest hole in the
Baltic (420 metres = 230 fathoms).

An unbroken ridge, extending from Stockholm to Hango in Finland, separates
the Baltic basin proper from the depression between Sweden and the Aland
Isles, to which the name Aland Haf has been given. North of the Aland Haf a
ridge defines the southern edge of another depression, the Bothnian Sea,
which in turn is separated from the most northerly division, the Gulf of
Bothnia, by a ridge across the narrow Quarken or Kvarken Strait. The
Gotland deep may be said to extend directly into the Gulf of Finland, an
arm of the Baltic, running eastwards for about 250 m., and separating
Finland from Esthonia. Between Esthonia and Courland is the Gulf of Riga, a
shallow inlet of roughly circular form, about 100 m. in diameter, and
nowhere more than 27 fathoms deep.

According to recent computations the total area