ance within the reach of the tide. Indeed, we found the same coral
till we began to approach the summits of the highest hills; and, it was
remarkable, that these were chiefly composed of a yellowish, soft, sandy
stone."[13] In the island of Vavau it was remarked by Captain Waldegrave
that the coral rock rises many feet above the present level of the sea,
and he adds: "The action of fire is visible on it, and we saw several
instances of its crystallisation."[14]

[11] T. West, _op. cit._ 95.

[12] Captain James Cook, _Voyages_, v. 344.

[13] Captain James Cook, _Voyages_, v. 381.

[14] Captain the Hon. W. Waldegrave, R.N., "Extracts from a
Private Journal," _Journal of the Royal Geographical Society_,
iii. (1833) p. 193.

The view that even the coralline islands of the Tongan archipelago have
been elevated by volcanic agency is not necessarily inconsistent with
Darwin's theory that coral reefs are formed during periods of
subsidence, not of elevation;[15] for it is quite possible that, after
being raised ages ago by volcanic forces, these islands may be now
slowly subsiding, and that it has been during the period of subsidence
that they have become incrusted by coral reefs. Yet the occurrence of
coral rocks, bearing all the marks of marine action, at considerable
heights above the sea, appears indubitably to prove that such a general
subsidence has been in some places varied by at least a temporary
elevation.

[15] Charles Darwin, _Journal of Researches, etc., during the
Voyage of the "Beagle"_ (London, 1912), pp. 471 _sqq._; Sir
Charles Lyell, _Principles of Geology_, Twelfth Edition (London,
1875), ii. 602 _sqq._; T. H. Huxley, _Physiography_ (London,
1881), pp. 256 _sqq._

In thus postulating elevation by volcanic action, as well as subsidence,
to explain the formation of the Tongan islands I am glad to have the
support of a good observer, the late Rev. Dr. George Brown, who spent
the best years of his life in the Pacific, where his experience both of
the larger and the smaller islands was varied and extensive. He writes:
"I have seen islands composed of true coralline limestone, the cliffs of
which rise so perpendicularly from the blue ocean that the natives have
to ascend and descend by ladders in going from the ocean to the top, or
vice versa. A large steamer can go so close to some of these cliffs that
she could be moored alongside of them in calm weather. It is