SOUTH MAHLOSMADULU. 381 



to tow us from place to place, and used the same for visiting the reefs and dredging. Our 

 work, however, had to be largely restricted to a belt 5 — 6 miles in width along the broad 

 south and south-east part of the bank. The season (Nov. 11 — 30) was that at the com- 

 mencement of the N. E. monsoon, when the currents gradually change completely round from 

 about W. S. W. to E. N. E. The current of the N. E. mon.soon sweeps through the Kardiva 

 channel with great force, but passes mainly to the south of Goifurfehendu. S. Mahlos is 

 rather affected by that across Fadifolu, and between that atoll and the Miladumadulu bank. 

 A part of this current rushes through the deep channels that divide the whole of Mahlos 

 into three banks, but .some sweeps down by Mabaru, and much sweeps over the bank. Currents 

 of 3 to 4 miles an hour were several times registered in the channels near Duravandu, but 

 they are of less importance in the more southern passages. It is possible, however, that in 

 the channels near Hitadu there may be powerful currents in the opposite monsoon. In corre- 

 spondence with these currents the bottom of the lagoon was everywhere in the part we visited 

 covered with hard sand, singularly barren of organic life. In the passages rock was found 

 either flat or — especially near Duravandu — extremely rough, the dredges constantly catching 

 up in living and dead masses of coral, etc. All this growth of living coral, however, might 

 be, judging from our experiences in other atolls, merely in local, isolated patches, though 

 certainly Mr Cooper's dredgings in the three passages north of Duravandu point to a general 

 upgrowth of the whole rim reef near its seaward margin. 



In regard to the land, it is evident that all or most of the reefs of the rim to the 

 south and east had at one time a broad line of elevated rock against the sea. This extended 

 on each more or less as a crescent, the two horns of which curved round for some distance 

 on either side against the dividing passages. Behind this there still exists on most reefs 

 a sandy islet. All such islands on the rim reefs, whether of sand or not, are generally washing 

 away on their seaward faces and growing outwards on their reefs towards the inner part of 

 the bank. On most of the reefs no definite conclusions were possible as to what causes the 

 rock owed its origin, but in Maduwari (p. 163 and Fig. 30) and Hitadu elevation was 

 clearly indicated. Further, no piling up of coral or of other reef material was anywhere found, 

 so that it is reasonable to conclude that the rock everywhere was formed by elevation. The 

 coarse and jagged appearance of the sand grains, that for some distance behind the rocky 

 belt form the land, leads me to believe that the outer parts of the sandy areas of the islands 

 largely owe their existence to the same change of level that formed the rock. 



The seaward slopes of the reefs follow the usual form, but the presence of raised rock 

 on the southern reefs, within 40 yards of their seaward edges, shows that their outward growth 

 since the elevation occurred cannot but have been very small. A more marked change may 

 be seen in points from the reefs having grown out into the passages at their seaward ends, 

 the narrowest parts of the channels into the bank and the broadest parts of the individual 

 reefs being generally in this neighbourhood. The bottom off these points is covered with corals, 

 and slopes not more steeply than the reef to seaward. The lines of raised rock pass gradually 

 round on the reefs along the sides of the passages, and do not continue out into these points. 

 It is hence a fair deduction that these points represent a fresh growth since the elevation 

 took place. Further there is every reason to believe that this growth is still going on, and 

 that it will ultimately provide our bank with a complete encircling reef. 



As to the lagoon reefs the account given of them in N. Mahlos (Chap. VI.) equally applies 

 to this bank. An unusual feature of the reefs of the islands from Madu to Duravandu is 



49—2 



