Zanzibar to the coast of Senegal is only thirty-five
hundred--say four thousand miles. Well, at the rate of two
hundred and forty miles every twelve hours, which does
not come near the rapidity of our railroad trains, by
travelling day and night, it would take only seven days to
cross Africa!"

"But then you could see nothing, make no geographical
observations, or reconnoitre the face of the country."

"Ah!" replied the doctor, "if I am master of my
balloon--if I can ascend and descend at will, I shall stop
when I please, especially when too violent currents of air
threaten to carry me out of my way with them."

"And you will encounter such," said Captain Bennet.
"There are tornadoes that sweep at the rate of more than
two hundred and forty miles per hour."

"You see, then, that with such speed as that, we could
cross Africa in twelve hours. One would rise at Zanzibar,
and go to bed at St. Louis!"

"But," rejoined the officer, "could any balloon withstand
the wear and tear of such velocity?"

"It has happened before," replied Ferguson.

"And the balloon withstood it?"