306 "ALBATKOSS" TROPICAL PACIFIC EXPEDITION. 



The reef flat is about 100 feet wide, and covered mainly by huge blocks 

 of Porites and Millepores separated by lanes of water ; the tops of the masses 

 of coral have died and are overgrown with many colored Nullipores. The 

 dead coral heads of the reef fiat were evidently once flourishing, but those now 

 alive are limited to the outer heads growing near the knolls of Nullipores 

 on the outer edge of the narrow reef flat we have just described. The 

 Nullipores are of a brilliant red, carmine or yellow color. The coral 

 heads have become united by the breaking off of the upper branches 

 and cemented with fragments of Nullipores. This reef flat is very similar 

 to the one we described at Gehh on the west coast of Menschikov atoll. 



The lagoon side of the south face of Rongelab is exposed to the full action 

 of the trades sweeping across the atoll ; they have a reach of about thirty- 

 five miles. The strength of the trades is shown by the high breakers seen 

 in the gap, to the eastward of the beach where we anchored. We found 

 a few coral heads in the lagoon, on the way to our anchorage. 



When lifting anchor we brought up a huge mass of white, dead coralline 

 Algae and coral mud formed from the agglomeration of fragments of dead 

 corals, shells, and beach rock fragments, but consisting principally of 

 coralline Algae and Nullipores, forming a sticky mortar covering the 

 bottom of the lagoon wherever we had an opportunity to examine it. This 

 conglomerate is formed in an inner sea, as it were ; it differs strikingly 

 from the conglomerate formed on the beaches, both on the sea face and 

 the lagoon face, a conglomerate made up of larger angular or worn 

 fragments of broken coral and of beach rock. 



On the east of Rongelab are a number of sandy islets and sand points 

 flanked by high steep beaches, edged with beach rock and topped with 

 low vegetation. The island to the west of the pass resembles the main 

 island ; its south shore extends in a long sand spit at the west end, 

 and the small sand islet to the north as well as the beach are both flanked 

 by beach rock conglomerate. 



