While the doctor was jotting down the result of this experiment, the loud report of a gun was heard close beside him. Kennedy had not been able to resist the temptation of firing at a huge hippopotamus. The latter, who had been basking quietly, disappeared at the sound of the explosion, but did not seem to be otherwise incommoded by Kennedy’s conical bullet.

“You’d have done better if you had harpooned him,” said Joe.

“But how?”

“With one of our anchors. It would have been a hook just big enough for such a rousing beast as that!”

“Humph!” ejaculated Kennedy, “Joe really has an idea this time—”

“Which I beg of you not to put into execution,” interposed the doctor. “The animal would very quickly have dragged us where we could not have done much to help ourselves, and where we have no business to be.”

“Especially now since we’ve settled the question as to what kind of water there is in Lake Tchad. Is that sort of fish good to eat, Dr. Ferguson?”

“That fish, as you call it, Joe, is really a mammiferous animal of the pachydermal species. Its flesh is said to be excellent and is an article of important trade between the tribes living along the borders of the lake.”

“Then I’m sorry that Mr. Kennedy’s shot didn’t do more damage.”

“The animal is vulnerable only in the stomach and between the thighs. Dick’s ball hasn’t even marked him; but should the ground strike me as favorable, we shall halt at the northern end of the lake, where Kennedy will find himself in the midst of a whole menagerie, and can make up for lost time.”