[part ir. 
886 ISLAND LIFE. 
it is much broader, and stretches out opposite Mozambique to a 
distance of about eighty miles. The Mozambique Channel varies 
from less than 500 to more than 1,500 fathoms deep, the shal- 
lowest part being where the Comoro Islands and adjacent shoals 
seem to form stepping-stones to the continent of Africa. The 
500-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 around 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 fiq.d the Chagos and Maidive coral atolls, 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 sub- 
merged islands, as shown in our map at p. 396, 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 con- 
siderably 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 is good proof of recent subsidence ; while 
we have no record of raised coral rocks inland which would 
certainly mark any recent elevation, because fringing coral reefs 
surround a considerable portion of the northern, eastern, and 
south-western coasts. We may therefore conclude that during 
