The lava
streams are covered with hummocks, and are rugged to a degree
which, geologically speaking, is not of easy explanation. The
intervening spaces are concealed with layers of pumice, ashes and
volcanic tuff. Whilst passing this end of the island at sea, I
could not imagine what the white patches were with which the whole
plain was mottled; I now found that they were sea-fowl, sleeping in
such full confidence, that even in mid-day a man could walk up and
seize hold of them. These birds were the only living creatures I
saw during the whole day. On the beach a great surf, although the
breeze was light, came tumbling over the broken lava rocks.
(PLATE 103. CELLULAR FORMATION OF VOLCANIC BOMB.)
The geology of this island is in many respects interesting. In
several places I noticed volcanic bombs, that is, masses of lava
which have been shot through the air whilst fluid, and have
consequently assumed a spherical or pear-shape. Not only their
external form, but, in several cases, their internal structure
shows in a very curious manner that they have revolved in their
aerial course. The internal structure of one of these bombs, when
broken, is represented very accurately in Plate 103.
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