to the sea-shore. {413}

[Illustration]

{414}

The sea around Madagascar, when the shallow bank on which it stands is
passed, is generally deep. This 100-fathom bank is only from one to three
miles wide on the east side, but on the west it is much broader, and
stretches out opposite Mozambique to a distance of about eighty miles. The
Mozambique Channel is rather more than 1,000 fathoms deep, but there is
only a narrow belt of this depth opposite Mozambique, and still narrower
where the Comoro Islands and adjacent shoals seem to form stepping-stones
to the continent of Africa. The 1,000-fathom line includes Aldabra and the
small Farquhar Islands to the north of Madagascar; while to the east the
sea deepens rapidly to the 1,000-fathom line and then more slowly, a
profound channel of 2,400 fathoms separating Madagascar from Bourbon and
Mauritius. To the north-east of Mauritius are a series of extensive shoals
forming four large banks less than 100 fathoms below the surface, while the
1,000-fathom line includes them all, with an area about half that of
Madagascar itself. A little further north is the Seychelles group, also
standing on an extensive 1,000-fathom bank, while all round the sea is more
than 2,000 fathoms deep.

It seems probable, then, that to the north-east of Madagascar there was
once a series of very large islands, separated from it by not very wide
straits; while eastward across the Indian Ocean we find the Chagos and
Maldive coral atolls, perhaps marking the position of other large islands,
which together would form a line of communication, by comparatively easy
stages of 400 or 500 miles each between Madagascar and India. These
submerged islands, as shown in our map at p. 424, are of great importance
in explaining some anomalous features in the zoology of this great island.

If the rocks of Secondary age which form a belt around the island are held
to indicate that Madagascar was once of less extent than it is now (though
this by no means necessarily follows), we have also evidence that it has
recently been considerably larger; for along the east coast there is an
extensive barrier coral-reef about 350 miles in length, and varying in
distance from the land from a quarter of a mile to three or four miles.
This seems to indicate recent subsidence; while we have no record of raised
coral rocks inland which would certainly mark any recent elevation, though
fringing coral reefs surround a considerable port