TEUK. 353 



Truk. 



Plates 191-193, 231, 232. 



Truk ^ is the largest atoll in the Carolines. The circumference of the 

 lagoon enclosed by the outer barrier reef is not less than 125 miles (PI. 231). 

 In our approach to Truk we followed much the track of the " Astrolabe and 

 Zelee," though we entered the lagoon of Truk through Aualap Pass, east of 

 Faleu, and steamed towards the northwest between Eiol and Udot Islands, 

 after being abreast Tsis Island. We could follow, as we passed, the in- 

 tricate passages formed between the spurs of the islands and the coral 

 reef flats which reach out from their sides. We anchored off the island 

 of Uola, the largest island in the eastern part of the atoll. 



As one enters the lagoon from the south, the appearance of this atoll 

 is most striking ; when once in the central part of the lagoon, after losing 

 sight of the barrier reef flat, facing the eastern cluster of islands (PI. 191, 

 figs. 3, 4), with the western cluster to the rear (PI. 193, figs. 1, 2), the 

 numerous peaks, rising, as it were, directly out of the sea (Pis. 191, 

 figs. 3, 4 ; 193, figs. 1-3), appear like summits of islands gradually sinking. 

 Had this atoll been among the first visited by us, it would have been 

 n.atural to explain its present condition as one due to subsidence. Yet 

 whenever the line of the barrier reef with its belt of islands and islets 

 thrown up on the outer reef flat again became well defined, the atoll at 

 once found its place among other similar but smaller atolls, the structure 

 of which we have explained by the mechanical action of the trades, of 

 atmospheric agencies, and of submarine erosion. 



The reef flats forming the great encircling barrier reef of Truk 

 are generally wide (PI. 231) ; they are broadest on the northern and 

 northeastern faces, gradually becoming narrower towards the southern 

 part of the eastern face, and quite nari-ow in parts of the southern 

 face. On the northern and eastern faces the barrier reef flat is covered 

 with a large number of low islands (PI. 191, figs. 1, 2) ; between the 

 disconnected portions of the encircling reef flat a number of deep passages 



1 A. Chart 982. 

 23 



