rrible heat.

"Don't hurry--open out slowly so as to spread the weight!" cried Sir
John; and the doctor and Ned obeyed; but Jack saw that at every step his
father's feet sank lower, and that his alpen-stick gave him no support,
but went right in.

"Do you hear me, Jack?" shouted Sir John.

"Yes, father, but I can't leave you," cried the lad. "Here, give me
your hand, or take hold of the end of my staff."

"Go on! Obey me, boy, or you will destroy us both," cried Sir John
sternly, and Jack continued to climb up the slope, finding it more and
more yielding, and as if below the ashes and stones there was a
quivering or bubbling going on.

"That's right! go on, Jack; go on," cried Sir John. "It isn't far now."

They pressed on with a horrible feeling of panic attacking them now, for
the quivering beneath them increased, the surface over which they toiled
was trembling, and several of the blocks they passed began to settle
slowly down.

"Only another fifty feet!" shouted the doctor. "Come on."

But at that moment a yell of warning came from the sailors, and Jack
looked round to see that the ashes where his father climbed up were
changing colour; then he noted that the slope was growing steeper and
steeper; and to his horror his father threw himself at full length and
began to crawl.

"Below there!" yelled Lenny. "Look out, Sir John."

"Below there! look out, Mr Jack," cried another sailor; and a couple of
ropes flew down the slope in rapidly opening rings, and so accurately
pitched that Jack caught his just as he felt that he was sliding
downward.

Before he could turn to look at his father the rope tightened, and he
was rapidly drawn up out of a heat that was terrible; but as he reached
the edge of the crater he wrenched himself round in time to see that Sir
John was nearly up; and the next minute he too was well over the side,
the doctor and Ned, who had reached the top unaided, coming up white and
trembling.

It was none too soon, for a minute later the slope down toward the pool,
which had been easy, had now become, from the sinking of the centre,
tremendously steep, and the pool itself suddenly began to spread out
more and more, till half the expanse below was covered with the
shimmering molten lava, and the heat became so intense that they were
all glad to retreat down the side.

"What an escape, my boy!" panted Sir John, as he grasped his son's arm.

"It was dreadful," whispered Jack. "But are