ised by
Mr. Butler in _Nature_, April 21, 1892.

CHAPTER IV.

THE SANTORIN GROUP.

[Illustration: Fig. 13.--Ideal Section through the Gulf of Santorin, to
show the structure of the submerged volcano.--_a._ Island of Aspronisi;
_b._ Island of Thera; 1. Old Kaimeni Island; 2. New Kaimeni Island; 3.
Little Kaimeni Island.]

(_a._) Before leaving the subject of European active volcanoes, it is
necessary to give some account of the remarkable volcanic island of
Santorin, in the Grecian archipelago. This island for 2000 years has
been the scene of active volcanic operations, and in its outline and
configuration, both below and above the surface of the Mediterranean,
presents the aspect of a partially submerged volcanic mountain. (See
Section, Fig. 13.) If, for example, we can imagine the waters of the sea
to rise around the flanks of Vesuvius until they have entered and
overflowed to some depth the interior caldron of Somma, thus converting
the old crater into a crescent-shaped island, and the cone of Vesuvius
into an island--or group of islands--within the caldron, then we shall
form some idea of the appearance and structure of the Santorin group.

_Form of the Group._--The principal island, Thera, has somewhat the
shape of a crescent, breaking off in a precipitous cliff on the inner
side, but on the outer side sloping at an angle of about fifteen degrees
into deep water. Continuing the curvature of the crescent, but separated
by a channel, is the island of Therasia; and between this and the
southern promontory of Thera is another island called Aspronisi. All
these islands, if united, would form the rim of a crater, in which the
volcanic matter slopes outward into deep water, descending at a short
distance to a depth of 200 fathoms and upwards. In the centre of the
gulf thus formed rise three islands, called the Old, New, and Little
Kaimenis. These may be regarded as cones of eruption, which history
records as having been thrown up at successive intervals. According to
Pliny, the year 186 B.C. gave birth to Old Kaimeni, also called Hiera,
or the Sacred Isle; and in the first year of our era Thera (the Divine)
made its appearance above the water, and was soon joined to the older
island by subsequent eruptions. Old Kaimeni also increased in size by
the eruptions of 726 and 1427. A century and a half later, in 1573,
another eruption produced the cone and crater called Micra-Kaimeni. Thus
were formed, or rather wer