f this
difficulty, other doubts would appear to suggest themselves as to the
applicability of Darwin's theory to coral formations in general. For
instance, it might be supposed that rain falling on a substance already
saturated with moisture, would flow off instead of sinking into it; and
that being of less specific gravity than salt water, it would fail to
"displace an equal bulk" of the latter. There are some extraordinary but
well attested statements of a thin layer of fresh water being found on
the surface of the sea, after heavy rains in the Bay of Bengal. (_Journ.
Asiat. Soc. Beng_. vol. v. p. 239.) Besides, I fancy that in the
majority of atolls and coral islands the quantity of rain which so small
an area is calculated to intercept would be insufficient of itself to
account for the extraordinary abundance of fresh water daily drawn from
the wells. For instance, the superficial extent of each of the
Laccadives is but two or three square miles, the surface soil resting on
a crust of coral, beneath which is a stratum of sand; and yet on
reaching the latter, fresh water flows in such profusion, that wells and
large tanks for soaking coco-nut fibre are formed in any place by merely
"breaking through the crust and taking out the sand."--_Madras Journal_,
vol. xiv. It is curious that the abundant supply of water in these wells
should have attracted the attention of the early navigators, and Cosmas
Indicoplenstes, writing in the sixth century, speaks of the numerous
small islands off the coast of Taprobane, with abundance of fresh water
and coco-nut palms, although these islands rest on a bed of sand.
(_Cosmas Ind_. ed. Thevenot, vol. i. p. 3, 20). It is remarkable that in
the little island of Ramisseram, one of the chain which connects Adam's
Bridge with the Indian continent, fresh water is found freely on sinking
for it in the sand. But this is not the case in the adjacent island of
Manaar, which participates in the geologic character of the interior of
Ceylon. The fresh water in the Laccadive wells always fluctuates with
the rise and fall of the tides. In some rare instances, as on the little
island of Bitra, which is the smallest inhabited spot in the group, the
water, though abundant, is brackish, but this is susceptible of an
explanation quite consistent with the experiments of Mr. Witt, which
require that the process of percolation shall be continued "during
_long_ periods and through _great masses of porous strata