m, they
found was the highest spot in the entire group.

CHAPTER ELEVEN.

AN IMPORTANT DISCOVERY.

From the point which they had now reached Sibylla and Ned commanded a
bird's-eye view of the entire harbour, with South Island--as it soon
came to be called--for a background, with the southern horizon showing
just clear of its highest portion. Ned was now able to form a very much
more correct idea of the entire locality than had before been possible;
and as he stood critically examining the two basins, a suggestion as to
their possible origin and that of the islands themselves presented
itself to his mind. Seen from where he then stood the group bore a very
strong resemblance to the crater of a long extinct volcano. To begin
with, the ridge-like summits of the islands swept round in a form that
was roughly circular, and they would have been continuous but for the
breaches or channels which separated the islands from each other. They
presented an appearance precisely similar to the rim of a volcanic
crater; and the inner and outer slopes of the islands were also strongly
suggestive of the inside and outside slopes of a crater. The two basins
conveyed the idea of two closely contiguous vents for the subterranean
fires, and the channels might very well be breaches in the sides of the
crater through which the molten lava had burst its way. And this theory
was confirmed by the colour of the water at the seaward extremities of
the several channels, which clearly indicated the existence of reefs
that might very well have been formed by the outflow. Some of these
reefs, it is true, were so deeply submerged that the sea did not break
over them at all, at least in fine weather such as then prevailed; this
being notably apparent in the case of the channel by which the _Flying
Cloud_ had entered the harbour. But the mouth of the north-east
channel, and that of the north arm of the south-east channel, were so
choked with rocks close to the surface that they showed nothing but a
wide expanse of white water. In a word, the more Ned thought about it
the more convinced he became that he was standing on the summit of a
volcanic mountain, the top only of which rose above the surface of the
sea. As to the period when the volcano had become extinct, Ned was not
scientist enough to form any opinion, but the whole aspect of the place
was such as to convince him that it must have been countless ages ago.

Having at length satis