30 ON CORAL HEEFS AND ISLANDS. 



another mass, similarly attached to the reef at base, observed on 

 Kawehe, (Yincennes Island.) It was six feet high above low 

 water level, and seven feet in its longest diameter. Below, it 

 had been worn like the one just described, though to a less ex- 

 tent. Another similar mass was eight feet high. Figure 3 rep- 

 resents a block six feet high 5 

 and ten feet in its longest di- 

 ameter, seen on Waterland ; it 

 was unattached below, and lay 

 with one end raised on a smal- 

 ler block. On Aratica, (Carl- 

 shoff,) others were observed. 

 One loose mass like the last was 

 •eight feet high and fifteen feet 

 in diameter, and contained at least a thousand cubic feet. Raraka 

 also afforded examples of these attached and unattached blocks, 

 some standing with their tops six feet above high-water mark. 



These masses are similar in character to many met with among 

 the fields of blocks just described, and differ only in having been 

 left on the platform instead of being transported over it. Some 

 of them are near the margin of the reef, while others are quite 

 at its inner limit. The third mass figured above was a solid con- 

 glomerate, consisting of large fragments of Astraeas and Madre- 

 pores, and contained some imbedded shells, among which an Os- 

 traea and a Cypraea were noticed. This is their usual character. 

 The other two were parts of large individual corals, (Porites;) 

 -but there was evidence in the direction of the cells that they did 

 not stand as they grew ; on the contrary, they had been up- 

 thrown, and were afterwards cemented with the material of the 

 Tock beneath them, probably at the time this rock itself was con- 

 solidated. Below some of the loose masses like figure 3, (as on 

 Aratica,) the platform was at times six inches higher than on 

 either side of the mass, owing to the protection from wear given 

 to the surface beneath it. These blocks are always extremely 

 rough and uneven, like those of the emerging land beyond ; and 

 the angular features are partly owing in both cases to solution 

 from rains or from the sea-water that may be dashed over them. 



It should be distinctly understood that these masses here de- 

 scribed were found isolated, and only at considerable intervals. 

 In no instance were they observed clustered. The loose blocks 

 and those cemented below had the same general character, and 

 must have been placed where they were by the same cause, 

 though it may have been at different periods. 



The shore of the lagoon is generally low and gently inclined, 

 yet in the larger islands, in which the waters of the lagoon are 

 much disturbed by the winds, there is usually a beach resem- 

 bling that on the seaward side, though of less extent. A plat- 



