196 "ALBATROSS" TEOPICAL PACIFIC EXPEDITION. 



In addition Haapai Banlc is covered with small low islands, scattered over 

 the bank for a distance of about forty miles (Pis. 217, 218) ; the bank 

 stretches in a northeast and southwestern direction, and has a greatest 

 width of about twenty-three miles. On the eastern face Haapai Bank is 

 flanked by a continuous angular line of reefs and islands, extending from 

 Haano Island on the north to Lima Island on the south. Some of the islands 

 are separated by narrow passages of considerable depth ;^ they are low, and 

 some of them broad, and appear to consist, like the lower parts of Tongatabu, 

 of elevated coralliferous limestone, which has gradually been denuded to the 

 level of the sea, while the islands on the western part of the bank rise to a 

 considerable height and are plainly terraced. 



The Haapai Bank is triangular (Pis. 217, 218), its depth varies from ten to 

 forty or fifty fathoms ; it drops off rapidly from 40 fathoms to 50 and 100 and 

 then to the 500-fathom line on the west. A number of the islands, patches, 

 and flats on the western part of the bank rise from comparatively deep water, 

 from water fully as deep as that of any part of the channels which separate 

 the banks, indicating that there are a series of more or less independent 

 summits on that part of the Haapai group. 



The larger islands flanking the eastern face of the northern jDart of 

 the Haapai Bank (Pis. 217, 218) are quite broad ; they are low, with low 

 cliffs of elevated coralliferous limestone edging their eastern face, or crop- 

 ping out on the western ; they are, according to Lister, from ten to twenty 

 feet, and slope very gradually towards the west. The broad and extensive 

 reef flats adjoining the islands and forming their continuation on the eastern 

 face of the bank, have either been elevated, or have been denuded from 

 larger limestone lands ; they are flanked by a narrow reef platform of 

 about 200 yards in width, edged by a narrow line of fringing reefs which 

 might, from its independence of the reef flat, be called a barrier reef. The 

 reef flat to the westward, the remnant of the former land area, is represented 

 only by irregular patches of coral or flats covered with sand bars and sand 

 ridges. 



The larger, islands flanking the east side of Haapai Bank, Haano, Foa, 

 Lifuka, and Uoleva occupy the greater part of the surface of the flats which 



^ Over thirty fathoms in Ava Mata Mata Vika, and nearly twenty fathoms south of Uoleva. 



