Holman’s warning came too late.  The rocky floor over which we had been running, dropped away from us.  I pitched forward after the youngster into a gulf of darkness, landed on my shoulder upon a mass of volcanic ash, and clutching vainly at the stuff, I rolled at tremendous speed down into the bowels of the earth.  From far above us came the sounds of uncontrolled merriment—­the high-pitched shrieks of a native rising above the deep bass laughter of Leith.

[Illustration]

CHAPTER XX

THE BLACK KINDERGARTEN

I thought we were a thousand years rolling down that slope of smothering ash.  It was a quicksand that melted beneath us.  We drove our arms into it, but the stuff slipped away like fine wood ash, and we went on and on.  I knew Holman was in front of me.  Occasionally a curse directed at Leith managed to slip out when his mouth was not filled with the smothering dust.  Once I shouted at him, and he answered the cry with a groan that told me how the happening had affected him.  The arch ruffian had checkmated us for the third time inside three days.

We struck the bottom at last, and, like moles, we clawed our way out of the pile of soft, feathery stuff that came streaming down upon us like a river, and for some minutes we were busy wiping the fluffy ash from mouth and eyes and ears.  It clung to us like down, and with each breath we drew it into our lungs till we coughed and sneezed from the irritation it produced.  Struggling forward, knee-deep in the fine, dry powder, we reached a spot that was practically clear, and for five minutes we were busy endeavouring to relieve our tortured lungs.

“How far did we roll?” asked Holman.

“About half a mile,” I replied.

“But straight, Verslun!  What do you think?”

“Over a hundred yards; I’m certain of that.”

“Well, I’m going to climb back.”

“You can’t do it!” I gasped.  “That stuff is like quicksand.”

“All the same I’m going to make a try.”

We stumbled back to the gigantic ash pile, and shoulder to shoulder we made a rush at the immense mountain down which we had rolled.  We couldn’t see it, but we felt it rise around us like a flood as our legs sank deeper.  It came up to our waists—­to our armpits, choking and smothering us.  Coming down we had rolled lightly over its surface, now our legs bored into it like rods, and we struggled vainly to move.  The pile was like a high snowdrift into which we sank deeper and deeper the more we struggled, and, worn out with our efforts, we fought our way clear of the smothering ash and made an attempt to review the situation.

“He’s beat us,” groaned Holman.  “He just trotted ahead of us till he had us on the verge of the thing, and then he side-stepped.  O God!  What asses we have been!”

“We did our best,” I said.

“Our best?” repeated Holman.  “And the man who tells you that he did his best as an excuse for failure should be shot, Verslun.”