174 J. STANLEY GARDINER. 
It is quite unnecessary to repeat the evidence and well-known views of Sir John Murray? 
and Admiral Sir W. L. Wharton* as to the action of marine currents in cutting down 
land and moving matter. Even by continental land where the action is that of currents 
due to the waves meeting an impediment, the shore platform tails commonly at 80 to 100 
fathoms off in a steep, the product of the backwash (see Plate VIII.). That the currents 
are strong and extend to considerable depths is evident from my being able to accurately 
note their directions down to 150 fathoms off the reefs. It was quite evident too in my 
soundings that the current was nearly equally strong in the passages right down to the 
bottom®. 
Of what rock the original land or bank was formed is entirely a matter of theory and 
a question, to which the geological study of the Indian continent has so far yielded no 
clue. It may have been a series of volcanic erupted masses as Sir John Murray suggested. 
If one supposes that the eruptions were submarine, that in effect the mountains were chiefly 
masses of loose volcanic matter, it would be easy to imagine even a greater erosion than 
to 150 or 200 fathoms. Sir John Murray considers that all oceanic islands are volcanic, 
regarding all others such as New Zealand, Madagascar and Seychelles as continental lands. 
Yet I may point out that with regard to most groups of coral islands there is no direct 
evidence to show that their foundations are volcanic. If they are really so, as the mountains 
of volcanic chains vary greatly in height, there would, it is reasonable to suppose, be a 
stray peak or two—central cores of hard lava round the craters—still remaining in the 
Maldives and Chagos. Further, so far as the Maldives are concerned there is no trace of 
any corresponding activity in the Indian Peninsula. I am hence rather inclined to believe 
that there was a connection with the other banks towards Madagascar, in fact that these 
reefs show the positions of the mountains of a great continental land, which once joined 
Ceylon and Madagascar, but the greater part of which has in past time subsided to great 
depths and left no trace at the present day. The existence of such a land in the past 
too is absolutely required to explain the distribution of both animals and plants‘. The 
current action would be, I consider, quite sufficiently powerful, aided in the first place by 
the disintegration of any subaerial land by heat, rain and other agencies, to cut down such a 
mountainous area, as I suppose to have existed, to the present level of our great Maldive plateau. 
It may be contended and perhaps truly that the separate banks are the remains of 
some of the peaks; that Kolumadulu and Male perhaps were the sites of mountains, which 
were cut down to a depth of 20, 40 or even 60 fathoms, and then built up by the 
reef-organisms to their present levels. I can scarcely regard this as probable on account 
of the great regularity of the common plateau and the regular precipitous slopes of the 
several banks on all sides. As already mentioned, there is no trace either of a central 
deeper valley nor of shallower valleys between the separate banks, the plateau being a 
1 Proc. Roy. Soc, Edin., vol. x., p. 507 et seq. 
2 Nature, vol. by. p. 390. 
3 My friend Mr Cameron points out that the influence of 
the friction of the bottom on the tidal waves and currents 
may be neglected. Horace Lamb (Hydrodynamics, p. 543, 
1893), after discussing the viscosity in periodic tidal force, 
summarised the matter as follows:—‘‘ This indicates how 
utterly insensible must be the direct action of viscosity on 
oceanic tides. There can be no doubt that the dissipation of 
energy by tidal friction takes place mainly through the 
eddying motion produced by the exaggeration of tidal cur- 
rents in shallow water.” 
4 Vide ‘The Anniversary Address to the Geological Society 
of London” by W. T. Blanford, F.R.S., February 21, 1890, 
pp- 58—69. It will be observed that, while rejecting the 
subsidence theory of Darwin as quite inadequate, I consider 
that the topographical conditions which made the formation 
of the coral reefs of this region possible, have probably owed 
their initiation to the sinking of a great continental land. 
