13 
1895.] C. F. Oldham —Physical Features of the Laccadives. 
north-eastern sides of the atolls with tremendous force, smashing and 
tearing the coral boulders off the edge and hurling them on to the cen¬ 
tre of the reef ; here then would be the foundation for the future island. 
The currents and tides and ordinary monsoon winds would then be suffi¬ 
cient to complete the remainder of the building up process. The strong 
winds of the south-west monsoon would cause sufficient sea to grind por¬ 
tions of the reef to sand, and this would be carried by the currents over 
and around the atoll to the lee side ; here eddy currents, due to the ob¬ 
struction of the atoll, would occur, depositing sand and debris to assist in 
raising the reef above high water ; seeds would be brought by the sea 
or deposited by the birds ; then man assisting, the once barren reef 
would develope into the present thickly planted coconut island ; each 
gale occurring would assist in adding to its size, and it may be that the 
parallel ridges noticed in some of the islands are due to the successive 
gales. 
The cause of the more vigorous outward growth of the reef to 
the southward artd westward, I have little doubt is due to the tides and 
currents. In these seas the currents vary with the monsoon, being 
nothing more than drift currents, except where their speed is accelerat¬ 
ed by some obstruction, as off the south coast of Ceylon. In the Lacca¬ 
dives, the observations of currents are exceedingly scanty. Those 
observed during the Investigator’s visits appeared to be entirely due to 
wind. 
The Admiralty current-chart, compiled from the greatest number of 
observations obtainable, shews that the currents are from east and north¬ 
east during the north-east monsoon, and from north north-west to south¬ 
west during the remainder of the year, this latter period lasting from 
March until October, or for eight months. The east-going currents are 
strongest, would cany most food to the coral reefs, and striking first on 
the western side of the atolls, would give up a portion of the food which 
they carry ; then the sand formed by the breakers would be carried 
from the weather side and be deposited to westward, tending to retard 
the coral growth on the eastern side and to assist in forming the present 
islands and islets. 
The tides are not strong in the Laccadives; the flood sets to the north¬ 
east past the northen reefs and east and south-east in the neighbourhood 
of the southern ones, that is, in a course at right angles to the length 
of the reefs. 
The flood would be a food-bearer to the reefs, aud therefore the tides 
would be another agent assisting the outward growth of the reefs to the 
south-west and westward. 
It is difficult to account for the positions of the openings to the Ja- 
