The thickest and most impenetrable smoke seemed to pervade the
narrow cavern!

"A Chinese smoke bomb!" sputtered and coughed Kennedy, as he
retreated a minute, then with renewed vigor endeavored to
penetrate the dense and opaque fumes.

We managed to go ahead still, but the intruder had exploded one
after another of his peculiar bombs, always keeping ahead of the
smoke which he created, and we found that under its cover he had
made good his escape, probably reaching the entrance of the cave
in the underbrush.

At the other end of the passageway, up in the living-room of the
cottage, the draught had carried large quantities of the smoke.
Elaine, Aunt Tabby and Joshua coughing and choking, saw it, and
opened a window, which seemed to cause a current of air to sweep
through the whole length of the passageway and helped to clear
away the fumes rapidly.

Long Sin, meanwhile, had started to work his way through the
bushes to reach the waiting car, with Wu, then paused and
listened. Hearing no sound, he replaced the helmet which he had
taken off.

Pursuit was now useless for us. With revolvers drawn, we crept
back along the passageway until we came again to the chamber
itself. There, on the floor, lay a bag of tools, opened, as though
somebody had been working with them.