Sect. II. 
ATOLLS. 
31 
Bennett informs me that the inclination of the bottom 
round Caroline atoll in the Pacific, is like that off 
Christmas island, very gentle. Off the Maldiva and 
Chagos atolls, the inclination is much more abrupt ; 
thus at Heawandoo Pholo, Lieut. Powell 1 found 50 and 
60 fathoms close to the edge of the reef, and at 300 
yards distance there was no bottom with a 300 yard 
line. Capt. Moresby informs me, that at 100 fathoms 
from the mouth of the lagoon of Diego Garcia he found 
no bottom with 150 fathoms : this is the more remark- 
able, as the slope is generally less abrupt in front of 
channels through a reef, owing to the accumulation 
of sediment. At Egmont Island, also, at 150 fathoms 
from the reef, soundings were struck with 150 fathoms. 
Lastly, at Cardoo atoll, only sixty yards from the reef, 
no bottom was obtained, as I am informed by Captain 
Moresby, with a line of two hundred fathoms ! The 
currents run with great force round these atolls, and 
where they are strongest, the inclination appears to be 
most abrupt. I am informed by the same authority, 
that wherever soundings were obtained off these is- 
lands, the bottom was invariably sandy : nor was there 
any reason to suspect the existence of submarine cliffs, 
as there was at Keeling Island. 2 Here, then, occurs a 
’ This fact is taken from a MS. account of these groups lent me 
by Capt. Moresby. See also Capt. Moresby’s paper on the Maldiva 
atolls in the Geographical Journal, vol. v. p. 401. 
2 Off some of the atolls in the Low Archipelago the bottom 
appears to descend by ledges. Off Elizabeth Island, which consists 
of raised coral-rock, Capt. Beechey (p. 45, quarto ed.) describes three 
ledges : the first slopes gently from the beach to a distance of about 
fifty yards ; the second extends two hundred yards with a depth of 
