NORTH MAHLOS BANK. 163 
feet, but it is difticult to decide whether there may not have been more action by rain 
in North Mahlos. It is possible also that the reef may have been more perfect before 
elevation at Minikoi than in Mahlos. It has been suggested to me too that the elevation 
at the two places need not have been contemporaneous, but this view I must absolutely 
reject. The elevation is found regularly around the tropical belt of the Pacific and Indian 
Oceans, and has probably not been due to an actual upheaval. It was rather, I think, 
dependent on a change of level in the ocean, brought about by the attraction of the 
water towards continental land and to the south polar region, On this view it is quite 
probable that there may be a real difference in different parts of the Maldives and in 
the Laccadives. The maximum height of the rock above the reef-flat is 9 feet in Mahlos, 
but in Miladumadulu it reaches 11 feet, and in Minikoi it is about 13 feet (p. 29). 
In Hulule, Male atoll, it is only 6 to 7 feet, and in Suvadiva and Addu 5 to 6 feet. 
Thus there would seem to be a real lessening of elevation to the south. The rainfall, 
it is true, also increases to the south, and perhaps accounts for some of the difference, 
but I would still consider that the greater part is really dependent on a less change 
of level. 
It remains now to consider the actual changes of the reefs and land since the change 
of level took place. In this connection it is necessary to call attention to the much 
steeper slope for the first 150 fathoms to seaward of the east reefs as compared with that 
off the west reefs. The character of the latter reefs is the same as those to the west 
of Minikoi and to the west of Funafuti'; the growth of all reef-building organisms—corals 
and nullipores—extremely vigorous and little or no sand. It is to be remembered also that 
the east side is protected to some extent by the neighbouring bank of Miladumadulu, the 
dirt from which must be injurious. The comparison of these reefs is hence with those 
to the south-east of Minikoi and off the east of the main island of Funafuti atoll. At 
the same time there can be no doubt, but that all the reefs are growing out on their 
seaward faces, and it may be assumed that such growth has been general at some time 
in the past off all the reefs on all sides, independently of any loss or other action that 
may be going on at the present time. The formation of the sandy areas of the islands 
may have been partially due to the elevation of flats within the original reefs as already 
mentioned, but is everywhere, I consider, mainly to be accounted for by the heaping up 
of sand by the winds and waves. The sand itself varies in coarseness, but none has the 
muddy character often found in sand-flats, nor could I find in it any traces of worm- 
tubes, branching nullipores and other organisms, which might be expected to have left 
some remains. 
That some of the original reefs were small faro, before they were elevated, is quite 
clear from the appearances of Raskateen and Hurudu, but the most striking case in the 
whole of Mahlos lies in Maduwari, almost its most southerly island (Plate XII. and fig, 30). 
The reef is about 14 miles long at its south or seaward side, the breadth of the bank 
being rather less. The island hes along the south side of the reef, and to the north of it 
is a sand-flat with about 4 feet of water at low tide, bounded by a surface reef. The south 
beach of the island is rocky, with two or three rows of pinnacles on the reef-flat. Above 
the beach is a rocky belt, which extends around the east and west ends of the island. 
' Vide “*The Coral Reefs of Funafuti, Rotuma and Fiji,” Proc. Camb. Phil. Soc., vol. 1x. pp. 417—503 (1898). 
