ANALYSIS OF THE SOUNDINGS TAKEN BY THE "AMRA." 21 



hundred and seventy-six fathoms (No. 41), with a bottom consisting of fine 

 coral sand, Pteropod shells, and masses of greenish Globigerinae. Four 

 miles from the starting-point, halfway across the channel, we sounded in 

 three hundred and seventy-four fathoms (No. 42), bringing up in the cup 

 fragments of white corals, coated with manganese. One and one-half miles 

 south of South Male Atoll (Hutekolu), we obtained two hundred and forty- 

 three fathoms (No. 43), bringing up in the cup small fragments of coral. 



The nature of the bottom of the main channels between the composite 

 atolls of the east or west chain varies greatly, some of them having, like 

 Wadu, Eastern Kudahuvadu, Fadiffolu to Miladummadulu channels, a hard 

 bottom swept clear ; in others the bottom is composed of Globigerinae and 

 Pteropods, as in Fulidu and Kardiva channels, and others of coral sand and 

 broken shells, as Ariyaddu, Wataru, and Gallandu, or coral sand and Glo- 

 bigerinae, as in Veimandu, West Kudahuvadu, Gaha Faro to Goifurfehendu. 



Line of soundings from Mulaku to Wataru Reef and to Felidu (PI. 8 b, 

 fig. 15). 



Halfway between Mulaku and Wataru Reef, in the centre of the chan- 

 nel, we found a depth of two hundred and fifty-three fathoms (No. 39). 

 The northern channel separating Wataru Reef from Felidu is somewhat 

 deeper than the southern one ; we obtained two hundred and eighty- 

 three fathoms (No. 40) in the centre of the channel, halfway from Wat- 

 aru Reef to Felidu Atoll, the bottom consisting of broken corals, shells, 

 and of coarse coral sand. 



Line of soundings across Ariyaddu Channel from Ariadu (Ari) to the 

 nearest point (clump of trees) in the northern face of North Nilandu 

 (PI. 8 b, fig. 14). 



One mile from Ariadu Pass we sounded in one hundred and forty-nine 

 fathoms (No. 10). In the centre of the channel we obtained two hundred 

 and thirty-one fathoms (No. 11), the bottom consisting of fragments of 

 corals and of coral sand and broken shells. One mile from North Nilandu 

 we sounded in one hundred and seventy-seven fathoms (No. 12), with 

 a coarse coral sand bottom, Ariyaddu Channel showing the same flat bottom 



