"How do you intend to act, then?" asked Kennedy.
"This way, Dick. You admit, no doubt, that if I succeed with the prisoner and throw away a quantity of ballast equal to his weight, nothing will be changed so far as the equilibrium of the balloon is concerned; but then if I want to secure a rapid ascent to escape this tribe of negroes, I must use stronger measures than the blow-pipe; now in throwing over this weight of ballast at the right moment I am sure to rise with great rapidity."
"That is evident."
"Yes; but there is great inconvenience in it. For instance, to descend slowly, I must lose a quantity of gas proportionate to the excess of ballast I shall have thrown away. Now this gas is a very precious commodity, but we must not regret the loss where the safety of a fellow-creature is concerned."
"You are right, Samuel, we must sacrifice everything to save him."
"Well, let us be up and doing. Dispose these bags so that they may be thrown down at once."
"But the darkness———"
"Will hide our preparations, and will not be gone until they are completed. Take care to have all the arms within reach. It may be necessary to give them a volley; we have one shot in the carbine, four in the two guns, twelve in the two revolvers—seventeen in all—which can be fired in a quarter of a minute. But we may not be obliged to resort to this. Are you ready?"
"We are," replied Joe.
The bags were arranged, and the arms laid ready for action.
"Good," said the doctor. "Keep a good look-out. Joe shall have the duty of throwing the ballast over, and Dick shall take up the prisoner, but nothing may be done without my orders. Joe, go and loose the grapnel and come back as quickly as possible."
Joe let himself slide down by the rope, and reappeared in a few minutes. The "Victoria" thus freed, floated in air, scarcely moving at all.
Meantime the doctor assured himself that there was a sufficient quantity of gas in the "mixing-chest" to support the blow-pipe, if necessary, without making it obligatory to
