Coral Reefs and Inlands. 149 



of the line of 180°, are, with one exception (Canton or Mary), 

 not over four miles long. The three more southern of the 

 Phoenix Islands (see Map, Plate I.), Gardner's, Hull's, and 

 Sydney, between 4° 25' S. and 4° 35 / S., are two to four 

 miles long, and have lagoons; five, including Phoenix, Birnie's, 

 and Kean's, between 3° 10' S. and 3° 30' S., and Howland and 

 Baker's, north of the equator, are a mile and a half and less 

 in length, and have depressions at centre, but no lagoons. 

 The depressions contain guano, and one of them, Kean's, has 

 much gypsum mixed with the guano *; Kean's and Phoenix 

 have a foot or two of water at high tide, the tide rising 6 feet. 

 Another of the number, Bnderbury's, is three miles long and 

 has a half-dried lagoon, which is very shallow and has no 

 growing corals f . To the north of these islands for fifteen 

 degrees of latitude the sea is an open one ; and in the next ten 

 degrees, to the line of the Hawaian Chain, the only islets not 

 marked doubtful are " Coral-Reef, A wash w and Johnston 

 Island. 



A similar gradation in size takes place in the Ellice, 

 Ratack, and many other groups of the ocean. Smallness of 

 size, and dried lagoon-basins, with occasionally a deposit of 

 gypsum from evaporated sea- water, are just the result that 

 should have come, by the Darwinian theory, from subsidence; 

 and gradation in size from gradation in the amount of subsi- 

 dence. The positions of the Union, Gilbert, Ratack, and 

 Ralick groups with reference to the Phoenix group are shown 

 on the Map, Plate I. All of the islands on the map are coral- 

 islands, and nearly all atolls; and the part of the encircling 

 reef marked by fine dots is under water at high tide. 



Adopting this view of the origin of these smallest of coral- 

 made islands, I readily accepted Darwin's second conclusion as 

 to a great central oceanic area of subsidence. The further 

 inference, also, was deduced, for reasons stated in my Report, 

 that the greatest amount of subsidence took place along 

 a belt stretching south-eastward from the southern half of 



* J. D. Hague, Amer. Journ. Sci. (II.) xxxiv. p. 242. Mr. Hague, in 

 his valuable paper on the Guano Islands of the Central Pacific, mentions 

 the existence of a bed of gypsum two feet thick under the guano of Jarvis 

 Island, another small equatorial island, eleven degrees east of the Phoenix 

 group. 



t Baker's Island has a height of 22 feet, according to Mr. Hague, 

 showing, he says, some evidence of elevation ; and Enderbury's I 

 found to be 18 feet in height, from which I inferred some elevation. But 

 Howland's, Birnie's, McKean's, Phoenix, Gardner's, Hull's, and Sydney 

 are not higher than ordinary atolls would be in a sea of 6-foot tide. 



The facts with regard to the "Reef" on the map, in long. 175° W. 

 and lat. 2° 40' S., I have been unable to learn. 



