360 "ALBATROSS" TROPICAL PACIFIC EXPEDITION. 



fringing reef, wliile scattered over the extensive shallow flat were growing 

 masses of Pocillipores. three or four species of Madrepores, and huge masses 

 of Porites elevated from three to four feet, killed in the centre, but still liv- 

 ing at the base. These formed luige agglomerations extending into deeper 

 water, where are found man}" massive species of Madrepores, with Mycedium, 

 Allopora, Pavonia. and masses of sponges, Gorgonians, and Alcyonarians. 



To the south of Uola rises Tolomen, a conical peak on Toloas, nearly 

 1200 feet in height, and still further south the cone of Umol, about 850 feet 

 in height. From the anchorage we could trace on the volcanic flats extend- 

 ing towards Tol numerous coral ledges, the remnants of the spurs which 

 once extended from the base of the many islands of Truk towards the 

 interior of the lagoon. We could also see the islands occupying the south- 

 west corner of Truk, the highest point of which (at Tol) reaches a height 

 of about 1200 feet. 



We left Truk by the northern passage. Steaming by the northern end of 

 Uola, we looked across the valley which separates the southern ridge from 

 Mount Ton Azan on the northern extremit}' of the island (PI. 231). The 

 neck connecting the two parts of Uola is a low reef flat, the remnant of 

 the elevated reef flat which once surrounded the greater part of this island. 

 To the north of Uola lies Gregoire Island ; to the westward, well on the 

 way to the north passage, lies Brongniart Island. Still further to the 

 north and east, on the outer edge of the barrier reef rim of Truk, we see 

 Gaudichaud, Quoj', Guinard, and a number of low well-wooded islands on 

 the flats to the east of Pis Island. The islands on the barrier reef flats 

 are connected by sand banks and sand bars, or by ridges and stretches of 

 beach rock conglomerate. Some of the barrier reef flats of the eastern and 

 northern part of the atoll have a width of nearly three miles. The outer 

 low islands are covered with magnificent vegetation. 



On the northwest face of the rim of the atoll there are onh' two islands. 

 On the northern face, running east to west, Pis Island, flanked by sand bars 

 and sand spits, occupies the whole length of the flat thrown up between two 

 passages leading out of the lagoon ; the principal passage is to the west of 

 Pis (PI. 193, fig. 4). Another smaller pass exists to the eastward of the 

 smaller islets on the northeast face of the reef, but it is so tortuous that it 



