every part of it. Once or twice Mark broke through, as one would fall
through rotten ice, when he found his shoes covered with a light dust
that much resembled ashes. In other places he broke this crust on
purpose, always finding beneath it a considerable depth of ashes,
mingled with some shells, and a few small stones.

That the water sometimes flowed into this crater was evident by a
considerable deposit of salt, which marked the limits of the latest of
these floods. This salt had probably prevented vegetation. The water,
however, never could have entered from the sea, had not the lava which
originally made the outlet left a sort of channel that was lower than
the surface of the outer rocks. It might be nearer to the real character
of the phenomenon were we to say, that the lava which had broken through
the barrier at this point, and tumbled into the sea, had not quite
filled the channel which it rather found than formed, when it ceased to
flow. Cooling in that form, an irregular crevice was left, through which
the element no doubt still occasionally entered, when the adjacent ocean
got a sufficient elevation. Mark observed that, from some cause or
other, the birds avoided the crater. It really seemed to him that their
instincts warned them of the dangers that had once environed the place,
and that, to use the language of sailors, "they gave it a wide berth,"
in consequence. Whatever may have been the cause, such was the fact; few
even flying over it, though they were to be seen in hundreds, in the air
all round it.




Chapter V.