THE GILBERT ISLANDS. 233 



local phenomena due to the shape of the land, the tides, and winds. In a 

 region whei'e the trades blow with regularity, the rehandling and moving 

 of all this material is due to the action of the prevailing wind ; the extent 

 and character of this depend almost entirely upon the position of the land 

 with reference to its direction. Where the northeast trade winds strike the 

 islands at a sharp angle, the effect of the swell will be to follow the coast 

 and haul around the two sides of the atoll. Sliould the atoll be wide 

 and long, the effect of the prevailing trades will be felt, not only on the 

 weather, but also on the lee side, inside of the lagoon. Considerable 

 material will also be handled and rehandled on the lagoon side of either 

 face, according to the strength of the sea, the direction of the winds, 

 and the length and breadth of the lagoon. If, on the contrary, the 

 trade winds should strike an island nearly at right angles to its weather 

 face, then a very decided lee is formed, even in the case of comparatively 

 small islands. In such a case the material is moved almost entirely on the 

 weather side, and the effect of the sea and wind on the lagoon shores of the 

 outer land rim is reduced to a minimum. During the changes of the trades 

 exactly the opposite will take j^lace ; but the winds then prevailing will 

 act only during a short time compared with that during which the long 

 season of the trades is eifective. 



To the west of the central part of the Gilbert Islands are situated 

 Paanopa and Nauru (PI. 234), isolated peaks of coralliferous limestone 

 elevated to a height of more than 200 feet. These islands are considered 

 as forming a part of the Gilbert group, though the most distant one, 

 Nauru, is about 300 miles from Nonuti, the nearest island of the Gilbert 

 chain. They are interesting, holding, as elevated islands, to the low 

 Gilbert atolls much the same relation which the elevated islands of 

 Makatea, of Niaii, and Rangiroa atoll hold to the low eroded Paumotus. 

 They give us, if not the key, at any rate a strong hint as to the probable 

 nature of the beds forming the substratum of the recent reef rocks of the 

 atolls of the Gilbert group. 



The sea face of Pleasant Island (Nauru) (PI. leO*") is not as regular as 

 that of Ocean Island ; its greatest length is three and three-fourths miles, 

 and its width varies fi'om two to two and three-fourths miles. The island 



