230 "ALBATROSS" TROPICAL PACIFIC EXPEDITION. 



less imperfect division wall between the sea face and the lagoons. Tlie 

 gaps between the buttresses of beach rock gave the sea face of Nukufetau 

 a very characteristic aspect. Immediately behind the belt of beach rock, 

 small islands or islets of sand and sand bars extend at right angles to the 

 general line of the shore, and form walls of sand ; these may little by little 

 become connected, and finally close up the gap, as we have seen it take 

 place in the Paumotus, and thus form connecting islands closing that part 

 of the land rim and preventing the sea from having access to the lagoon. 

 Some of the reef platform sand bars extending towards the lagoon at right 

 angles to the outer islands are of considerable length. The reef platform 

 of Nukufetau is very similar to that of Funafuti, growing knolls of Nulli- 

 pores and Pocillipores forming its outer raised edge. 



On the north end of the east face of Nukufetau are indications of 

 former gaps now nearly closed ; they are apparent from the aspect of the 

 different parts of the outer shingle beach, — it is quite white and fresh 

 towards the gap, while immediately behind it, or rather on its northern 

 side, the shingle is dark and weathered. On the chart only seven gaps 

 are indicated ; we noticed nine. I would call attention to the remarkable 

 position of ten of the small islands, which follow in rapid succession, and 

 flank the gaps from the point marked A on the chart (PI. 212, fig. G). 



On the lagoon side of Nukufetau the shore is a succession of short sand 

 reaches of fine coral sand, with here and there a low stretch of beach rock. 

 The islands of the land rim all have on their steep sea faces more or less 

 extensive tracts of black shingle above the beach rock ; owing to the 

 narrowness of the outer land rim, the shingle often extends inland far 

 enough to connect with the fine sand of the lagoon beaches. The depth 

 of the lagoon of Nukufetau is said to vary between sixteen and twenty 

 fathoms. 



From Nukufetau we made for Niutao,* a nearly round island, about 

 one and a fourth miles in diameter, surrounded by a narrow fringing 

 reef. It has a small shallow lagoon, nothing but a brackish water sink. 

 The island of Niutao represents a stage in which an incipient sink has been 

 formed in the central part of the island. The sink of Niutao is probably 



1 A. Chart 987. 



