He went swiftly up the staircase and passages which led to the
observatory as he spoke.

The scene that met their eyes on reaching the ledge or plateau was
sublime in the extreme, as well as terrific.

"As I thought," said Van der Kemp, in a low tone. "It is Perboewatan
that has broken out."

"The cone from which I observed smoke rising?" asked Nigel.

"The same. The one over the very centre of the old crater, showing that
we were wrong in supposing it to be extinct: it was only slumbering. It
is in what vulcanologists term moderate eruption now, and, perhaps, may
prove a safety-valve which will prevent a more violent explosion."

That the cone of Perboewatan was indeed in a state of considerable
activity, worthy of a stronger term than "moderate," was very obvious.
Although at a distance, as we have said, of four miles, the glare of its
fires on the three figures perched near the top of Rakata was very
intense, while explosion after explosion sent molten lava and red-hot
rocks, pumice, and dust, high into the thickening air--clouds of smoke
and steam being vomited forth at the same time. The wind, of which there
was very little, blew it all away from the position occupied by the
three observers.

"What if the wind were to change and blow it all this way?" asked Nigel,
with very pardonable feelings of discomfort.

"We could return to the cavern," said the hermit.