102 NOTES ON THE CAVES OF FIJI, 



to see huge isolated masses of growing coral. As these masses 

 expand, there is a tendency for the isolated patches to coalesce 

 by fusion of the growing walls. Withal, however, channels are 

 frequently left between the clumps, probably to permit of circu- 

 lating waters conveying nutriment to all. The coalescence or 

 fusion of the expanding growths is most marked towards the sea 

 level, the tendency being to form arches overhead and to leave a 

 series of anastomosing canals below, broadening here and there 

 into chambers. Nullipores also help considerably in the work 

 of solidif3ang the mass and the closing in of the overhead 

 growths. 



The appearance of the structure just described, viewed from 

 a short distance, is that of a solid reef-platform flush with the 

 sea level. 



The study of such fringing reefs as those of Taviuni (Somo 

 Somo Strait), Mango, Yatu Vara, Lakemba and Kambara will 

 illustrate the foregoing remarks. 



Prof. David, of Sydney University, and Mr. C. Hedley,* of the 

 Australian Museum, mention the arching over of the submarine 

 channels of Funafuti by coral, nullipore and allied growths. 



On the Tonga Tabu coast, numerous " blow-holes " occur 

 in the reefs. These consist of long submarine conduits in the 

 fringing coralline limestone mass, opening out to the sk}^ by con- 

 stricted orifices, t Into the wide mouths of these tunnels the sea 

 dashes, and becoming confined as the way becomes narrower, is 

 dashed into the air as spraj'' by the on-rushing water behind. 



Prof. David mentions similar, though smaller, occurrences at 

 Funafuti. 



At Wangava, in southern Lau, a central salt lagoon exists^ 

 shut in from the sea on all sides by high limestone cliffs. The 

 tide is said to rise in the lagoon, thus showing its connection with 

 the outer sea b}'' a long, submarine passage. 



*C. Hedley, Natural Science, xii., 1898, p. 177. 

 t For this information we are indebted to Mr. J. Martin of Auckland. 



