baobab—an isolated tree in the midst of this desert region.
"It is all over," said Kennedy.
"And within a hundred paces of the river," said Joe.
The three unfortunate travelers descended, and the doctor dragged his two companions to the Senegal.
At this moment they heard a long sullen roar proceeding from the direction of the river, and when they reached the bank Ferguson recognized the cataracts of Gouina. Not a boat upon the river—not a living being to be seen.
The Senegal, 2,000 feet wide, fell here a height of 150 feet with a sonorous roar. It flowed from east to west, and the line of rocks that barred its course stretched from north to south. In the midst of the fall the rocks assumed strange forms, like some antediluvian animals petrified in the midst of the water.
The utter impracticability of this gulf was evident. Kennedy could not restrain a gesture of despair.
But Doctor Ferguson with his old energy cried out, "All is not yet lost!"
"I know that well," replied Joe, with that confidence in his master that never deserted him.
The sight of the dry grass had inspired the doctor with a bold idea. It was the only chance of safety. He drew his companions rapidly towards the balloon.
"We are at least an hour ahead of those robbers," he said; "let us lose no time, my friends; collect a quantity of this dry grass, at least 100 lbs. weight."
"For what purpose?" asked Kennedy.
"I have no more gas, so I will cross the river by means of hot air."
"Ah! my brave Samuel," cried Kennedy, "you are indeed a great man."
Kennedy and Joe set to work, and soon an enormous heap of grass was collected close to the tree. Meantime the doctor had enlarged the opening at the lower part of the balloon and had taken care to let all the hydrogen escape by the valve; he then piled some of the dry grass under the envelope and set fire to it.
A short time suffices to dilate a balloon with hot air; a heat of 180° is sufficient to diminish the weight of the air one-half by rarefaction, so the "Victoria" soon began to reassume her rounded appearance. There was no lack of
