Sect. III. 
MALDIVA ATOLLS. 
45 
another, and the great included expanse of water has a 
depth of between 250 and 300 feet. The smaller atolls 
in this group differ in no respect from ordinary ones ; 
hut the larger ones are remarkable from being breached 
by numerous deep-water channels leading into the 
lagoon ; for instance, there are 42 channels through 
which a ship could enter the lagoon of Suadiva. In 
the three southern large atolls, the separate portions of 
reef between these channels have the ordinary structure 
and are linear ; but in the other atolls, especially the 
northern ones, these portions are ring-formed like 
miniature atolls. Other ring- formed reefs rise out of 
the lagoons, in the place of those irregular ones which 
ordinarily occur there. In the reduction of the chart 
of Mahlos Mahdoo (Plate II. fig. 4), it was not found 
easy to define the islets and the little lagoons within 
each reef, so that the ring- formed structure is very im- 
perfectly shown : in the large published charts of Tilla- 
dou-Matte, the appearance of these rings, from stand- 
ing further apart from each other, is very remarkable. 
The rings on the margin are generally elongated ; 
many of them are three, and some even five miles in 
diameter ; those within the lagoon are usually smaller, 
few being more than two miles across, and the greater 
number rather less than one. The depth of the little 
lagoon within these small annular reefs is generally from 
five to seven fathoms, but occasionally more ; and in Ari 
atoll many of the central ones are twelve, and some 
even more than twelve fathoms deep. These rings rise 
abruptly from the platform or bank on which they 
