

182 J. STANLEY GARDINER. 
that others, through which tide and current particularly sweep, may have been and are being 
cleared out and deepened. 
It remains then to consider the reef-platform, which slopes gradually down to the 
commencement of the steep at about 40 fathoms. Why does not the whole grow up as a 
wall to the surface? To this question it is hard to give any answer on account of our 
ignorance of this slope, of what even its surface is like and what covers it. We are not 
in a position to theorise about it, but I should not suppose that the greater part of it 
came into existence contemporaneously with that of the foundation-bank. It is, so far as 
I am aware, a feature of all surface oceanic reefs in both the Pacific and Indian Oceans, 
and varies little in depth and breadth. There is no reason to suppose that the original 
shoals had any such tailing off. In the Maldives I did not particularly investigate this 
platform, but my soundings were sufficient to show that it is fairly regular on all sides 
of all banks save towards the interior of our plateau. In fact it was regular against all 
parts of the banks that were fairly freely exposed to the ocean. Off the west of Fadifolu 
I endeavoured for a short distance to place in both the 50 and 100 fathom lines. The 
two lines were generally separated from one another by no more than the length of my 
whale-boat, the slope from one to the other being certainly over 75°. I hence restricted 
myself to observing the 50 fathom line. It varied inside the banks from 50 to 300 yards 
from the edge of the reef-flat, in the majority of places being less than 100 yards. The 
steep generally commenced at about 20 fathoms, hence much below the depth usual outside 
atolls. This difference indicates that there is some action, much stronger outside the atolls, 
that forms this platform. This I conceive to be the current action, largely set up by the 
waves, and it is to it that I would look for an explanation of the shallow slope. The 
oncoming waves carry a large quantity of water against the reef, the most of which is 
thrown back in a deeper current, sweeping down the slope (see p. 24). The strength of 
this, weather conditions being constant, will depend on the exposure of the reef to the sea 
and on the height to which it rises in the water. For our purposes the reef may be 
assumed to reach the surface as in the Maldive banks. There is left then the question of 
exposure, which would naturally be much less on the inner sides of the banks. The outgoing 
currents would be less strong on the inner sides, and material would be carried out to a 
lesser depth than on the seaward sides. The quantity of lime thrown over the steep on 
the outer side would be very much greater than on the inner side. The depth at the 
edge of the reef-platform I would regard as the depth to which the current can sweep 
out the heavier masses of lime from the reef above. A considerable part of the reef to 
seaward might then have been formed of masses, piled up by this means. Against the 
deep channels between the several banks the strong currents would preserve for a long time 
the original, almost perpendicular slope, and from the lesser growth and protected situation 
within the bank the platform would be of less definite form and the original slope would 
be preserved. The Laccadive banks also support this view, in that the reef-platform on the 
west side of the reefs is of the regular slope and breadth, while on the east, which is 
protected by the Indian Peninsula, it is usually almost non-existent or else very narrow 
(Plate VILL). 
The matter in this chapter is, I fear, so extremely complicated on account of the varied 
conditions on the banks that it does not lend itself to the formulation of conclusions in a 
brief set of words. I may, however, present some of my views as to the formation of the 
