1898.] Funafuti, Rotuma and Fiji. 425 



water by means of a chisel, show clearly its constituents. In the 

 pools of the rough zone, referred to above, and on the reef-flat 

 slabs may be here and there raised by a crowbar, used as a lever. 

 These are found to have been fixed on to the rock below by 

 means of the living bodies of Tunicata and Porifera, growing to 

 both, while the spaces between them abound with Polychaeta 

 Gephyrea, Mollusca and Echinodermata. These slabs, and indeed 

 the solid rock elsewhere, are in most places much bored by worms, 

 so that this formed perhaps my most prolific collecting ground 

 for animals ; a considerable amount of muddy sand, formed by 

 these animals, under the rocks is a general feature. Some of 

 these slabs have been but recently thrown into their present- 

 positions, and are being consolidated on to the rock below them. 

 Many others, on the contrary, which could only be raised by 

 breaking the rock itself, seemed to be due rather to the inwash 

 of the sea, perhaps removing from under the harder coral, or 

 nullipore remains, a layer of sandy or softer rock, which had 

 formerly fixed them to the rock below. Probably both actions 

 are going on at the same time, the former in the pools of the 

 rough zone, lying immediately under the hurricane beach, and 

 the latter on the reef-flat outside its limits. That the effect of 

 this latter may in time be very considerable was indicated by the 

 whole beach on the weather side, after a strong easterly gale, 

 being to some extent strewn with slabs, which, on investigation, I 

 found to have come from the reef-flat close to the rough zone. 



The ordinary range of the tide at springs is 6^ feet. At high 

 tide the hurricane beach at its base is covered with 4 feet of 

 water ; in the rough zone there is a fall of about one foot, and a 

 sharp fall from this zone of one foot to the reef-flat. The reef-flat 

 is itself hollowed out to some extent so that it usually has about 

 8 inches of water on it, but is at the same time cut off from the sea 

 by the rim of the reef, which stands up about one foot above low 

 tide. The outer edge is much broken up by fissures (Fig. 2), 

 which often run for 20 yards or more straight into the reef: 

 these are joined together to some extent by cross fissures, so that 

 the rim at low tide appears to consist of a number of great more 

 or less rectangular flat masses projecting 1 — 2 feet above the 

 reef-flat. These are arranged so that there is a distinct edge 

 running along fairly evenly, but there are outside this on the 

 weather face of the atoll a number of similar masses extending 

 outwards for 8—10 yards with a depth over them of 2 — 3 feet 

 at low tide. These masses can be clearly seen at low springs, 

 after the backwash which precedes a breaker, and form the proper 

 edge of the reef. Off this line there is a sudden fall to a depth 

 of 3 — 4 fathoms : in places, however, there is no such fall and 

 no proper edge, but a succession of masses and buttresses at 



