46 PERCY SLADEN TRUST EXPEDITION, 
N.W.end. The points which form the entrance are called by Capt. Blair the E. and W. 
points, between them three islands are situated.” 
This atoll, the position of which was first definitely fixed by the Abbé Rochon in 1769, 
is, as the above description implies, a typical atoll of great size with its lagoon extra- 
ordinarily closed in by land. We anchored opposite Minni-Minni, and from that centre 
explored the whole atoll, one of us (Cooper) taking the lagoon, which was thoroughly 
dredged, and the smaller islands, while the other (Gardiner) zigzagged round the 
whole island from the north-east point round the south end to about 2 miles above 
Pt. Marianne. We both visited the darachois or backwaters of the lagoon, of which 
there are seven on the south-east side, extending into the land. Horsburgh’s description, 
which we had not then seen, is wonderfully accurate, but be neglects to mention the 
great sand-ridge which extends almost completely round the island on its outer side; 
it is evidently formed by blown sand, and at the north-east end breaks up into a series 
of barren dunes varying up to 30 or 40 feet in height. Outside this the reef forms a 
typical flat 80 to 150 yards broad, the shore behind being either rocky or sandy, the latter 
when we were there having a piled-up ridge at high-tide level over a foot broad, formed 
of dead “ Portuguese men-of-war” (Physalia) and the blue-shelled Zanthina, which is 
floated over the whole ocean by air-chambers in the mucous secretion of the foot. 
Our observations on the rim of land were carried out mainly in view of its formation 
and its present and past changes. We found evidence of the land having been divided 
by sea in places. These we do not consider due to inundations of the sea, but rather to 
the atoll rim having been covered by a series of separate islands, which subsequently 
became united together. To seaward there seemed to be but little loss going on, though 
undoubtedly the island formerly extended out for some distance on the reef-flat. 
Against the lagoon, however, it was very different, the shore often ending in small 
cliffs or being strewn with fallen timber, evidence of rapid encroachment from the sea. 
It has no reef-flat, but either tails off gradually or has a sandy flat. In the lagoon, 
which has a maximum depth of 17 fathoms, one would not perhaps expect to find much 
life, but so far from this being the case its dredging turned out to be singularly rich in 
every way as compared to Salomon. Porites and a few other corals occur even at its 
southern extremity, where the change of water produced by the tides is but slight * 
Algze, too, with the exception of the massive Lithothamnia, are more abundant here than 
anywhere else in the Chagos, and it is evident that the conditions are very suitable for 
their growth. Perhaps the dead matter carried from the land into the lagoon produces 
here a sufficiency of carbonic acid for both algze and corals (which feed on commensal 
algee). These would then in their turn liberate enough free oxygen for themselves and 
for a rich variety of animal life as well. 
The present settlements are at East Point and at Point Marianne on the middle of the 
east and west sides of the island respectively. Everywhere coconuts are planted, and 
there are from each settlement cart-tracks running north and south, boats being used 
only for the south end of the atoll. The island belongs to the same company as Peros, 
* There is about two hours’ difference between the tides of the outer and inner sides of the island at its 
south end. 
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