30 ATOLLS. Ch. I. 



to differ, for this officer ! informs me that all the 

 soundings, even the deepest, were on coral, but he 

 does not know whether dead or alive. The slope 

 round Christmas atoll (Lat. 1° 4' N., 157° 45' W.), de- 

 scribed by Cook, 2 is considerably less ; at about half 

 a mile from the edge of the reef, the average depth was 

 about fourteen fathoms on a fine sandy bottom, and at 

 a mile, only between twenty and forty fathoms. It has 

 no doubt been owing to this gentle slope, that the strip 

 of land surrounding its lagoon, has increased in one 

 part to the extraordinary width of three miles ; it is 

 formed of successive ridges of broken shells and corals, 

 like those on the beach. I know of no other instance 

 of such width in the reef of an atoll ; but Mr. F. D. 

 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 3 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 Grarcia he found 

 no bottom with 150 fathoms: this is the more remark- 



1 I must be permitted to express my obligation to Captain Beechey, 

 for the very kind manner in which he has given me information on 

 several points, and to own the great assistance I have derived from his 

 excellent published work. 



2 Cook's Third Voyage, vol. ii. chap. 10. 



3 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. 



