throb.

Jack Everson was sensible that through this medley of strange noises
there was one sound that was continuous and never changing. So faint
that at first he and Wharton failed to notice it, it now impressed
itself too distinctly upon his consciousness for him to be mistaken.
It was a low, steady hum or moaning, such as the traveller hears when
miles inland from the ocean. He could not identify it, though he made
several guesses, and was still speculating unsatisfactorily, when he
received a startling reminder that there was a new peril at his very
feet.

The first notice was a faint purring sound, as if made by a gigantic
cat, accompanied by a rustling of the vegetation scarcely a dozen feet
away. He instantly grasped his rifle with both hands and was alert.
It was impossible to distinguish ordinary objects in the gloom, but
suddenly two small circles glittered with a greenish light and the
purring was succeeded by a low, cavernous growl. Then it all became
clear to him: a royal Bengal tiger was stealing upon the boat and was
probably gathering himself for a leap at that very moment.

Had all the occupants been asleep the frightful terror would have
played sad havoc with them before they could defend themselves. As it
was, it looked as if more than one fatality must follow his attack.

But for that phosphorescent gleam of the brute's eyes Jack Everson
would not have been able to locate him, but the glow of the two objects
defined the outlines and locality of the horrible thing as unmistakably
as if the sun were overhead. The occasion was one in which everything
depended upon promptness. The tiger was likely to shift his position