The doctor ascertained the height of the lake above the level of the sea, as it had been determined by Captain Speke, say three thousand seven hundred and fifty feet.
“Here we are, then, on an island!” said Joe, scratching as though he’d tear his nails out.
“We could make the tour of it in a jiffy,” added Kennedy, “and, excepting these confounded mosquitoes, there’s not a living being to be seen on it.”
“The islands with which the lake is dotted,” replied the doctor, “are nothing, after all, but the tops of submerged hills; but we are lucky to have found a retreat among them, for the shores of the lake are inhabited by ferocious tribes. Take your sleep, then, since Providence has granted us a tranquil night.”
“Won’t you do the same, doctor?”
“No, I could not close my eyes. My thoughts would banish sleep. To-morrow, my friends, should the wind prove favorable, we shall go due north, and we shall, perhaps, discover the sources of the Nile, that grand secret which has so long remained impenetrable. Near as we are to the sources of the renowned river, I could not sleep.”
Kennedy and Joe, whom scientific speculations failed to disturb to that extent, were not long in falling into sound slumber, while the doctor held his post.
On Wednesday, April 23d, the balloon started at four o’clock in the morning, with a grayish sky overhead; night was slow in quitting the surface of the lake, which was enveloped in a dense fog, but presently a violent breeze scattered all the mists, and, after the balloon had been swung to and fro for a moment, in opposite directions, it at length veered in a straight line toward the north.
Dr. Ferguson fairly clapped his hands for joy.
“We are on the right track!” he exclaimed. “To-day or never we shall see the Nile! Look, my friends, we are crossing the equator! We are entering our own hemisphere!”