st of the lagoon to
the depth of nearly 200 feet. The bottom of the lagoon, at the depth of
101 1/2 feet from sea-level, was found to be covered with remains of the
calcareous, green sea-weed Halimeda, mingled with many foraminifera; but
at a depth of 163 feet from the surface of the lagoon the boring tools
encountered great masses of coral, which were proved from the fragments
brought up to belong to species that live within AT MOST 120 feet from
the surface of the ocean, as admitted by all zoologists. ("The Atoll
of Funafuti; Report of the Coral Reef Committee of the Royal Society",
London, 1904.)

Darwin's theory, as is well known, is based on the fact that the
temperature of the ocean at any considerable depth does not permit of
the existence and luxuriant growth of the organisms that form the reefs.
He himself estimated this limit of depth to be from 120 to 130 feet;
Dana, as an extreme, 150 feet; while the recent very prolonged and
successful investigations of Professor Alexander Agassiz in the Pacific
and Indian Oceans lead him also to assign a limiting depth of 150 feet;
the EFFECTIVE, REEF-FORMING CORALS, however, flourishing at a much
smaller depth. Mr Stanley Gardiner gives for the most important
reef-forming corals depths between 30 and 90 feet, while a few are found
as low as 120 feet or even 180 feet.

It will thus be seen that the verdict of Funafuti is clearly and
unmistakeably in favour of Darwin's theory. It is true that some
zoologists find a difficulty in realising a slow sinking of parts of the
ocean floor, and have suggested new and alternative explanations: but
geologists generally, accepting the proofs of slow upheaval in
some areas--as shown by the admirable researches of Alexander
Agassiz--consider that it is absolutely necessary to admit that this
elevation is balanced by subsidence in other areas. If atolls and
barrier-reefs did not exist we should indeed be at a great loss to frame
a theory to account for their absence.

After finishing his book on Coral-reefs, Darwin made his summer
excursion to North Wales, and prepared his important memoir on the
glaciers of that district: but by October (1842) we find him fairly
settled at work upon the second volume of his "Geology of the
'Beagle'--Geological Observations on the Volcanic Islands, visited
during the Voyage of H.M.S. 'Beagle'". The whole of the year 1843 was
devoted to this work, but he tells his friend Fox that he could "manage
only