Take care to have all our weapons close at hand. Perhaps we may have to fire; so we have one shot in the rifle; four for the two muskets; twelve in the two revolvers; or seventeen in all, which might be fired in a quarter of a minute. But perhaps we shall not have to resort to all this noisy work. Are you ready?"

"We're ready," responded Joe.

The sacks were placed as requested, and the arms were put in good order.

"Very good!" said the doctor. "Have an eye to every thing. Joe will see to throwing out the ballast, and Dick will carry off the prisoner; but let nothing be done until I give the word. Joe will first detach the anchor, and then quickly make his way back to the car."

Joe let himself slide down by the rope; and, in a few moments, reappeared at his post; while the balloon, thus liberated, hung almost motionless in the air.

In the mean time the doctor assured himself of the presence of a sufficient quantity of gas in the mixing-tank to feed the cylinder, if necessary, without there being any need of resorting for some time to the Buntzen battery. He then took out the two perfectly-isolated conducting-wires, which served for the decomposition of the water, and, searching in his travelling-sack, brought forth two pieces of charcoal, cut down to a sharp point, and fixed one at the end of each wire.

His two friends looked on, without knowing what he was about, but they kept perfectly silent. When the doctor had finished, he stood up erect in the car, and, taking the two pieces of charcoal, one in each hand, drew their points nearly together.

In a twinkling, an intense and dazzling light was produced, with an insupportable glow between the two pointed ends of charcoal, and a huge jet of electric radiance literally broke the darkness of the night.

"Oh!" ejaculated the astonished friends.

"Not a word!" cautioned the doctor.

CHAPTER TWENTY-SECOND.

The Jet of Light.--The Missionary.--The Rescue in a Ray of Electricity.--A Lazarist Priest.--But little Hope.--The Doctor's Care.--A Life of Self-Denial. --Passing a Volcano.

Dr. Ferguson darted his powerful electric jet toward various points of space, and caused it to rest on a spot from which shouts of terror were heard. His companions fixed their gaze eagerly on the place.

The baobab, over which the balloon was hanging almost motionless, stood in the centre of a clearing, where, between fields of Indian-corn and sugar-cane, were seen some fifty low, conical huts, around which swarmed a numerous tribe.

A hundred feet below the balloon stood a large post, or stake, and at its foot lay a human being--a young man of thirty years or more, with long black hair, half naked, wasted and wan, bleeding, covered with wounds, his head bowed over upon his breast, as Christ's was, when He hung upon the cross.

The hair, cut shorter on the top of his skull, still indicated the place of a half-effaced tonsure.

"A missionary! a priest!" exclaimed Joe.

"Poor, unfortunate man!" said Kennedy.

"We must save him, Dick!" responded the doctor; "we must save him!"

The crowd of blacks, when they saw the balloon over their heads, like a huge comet with a train of dazzling light, were seized with a terror that may be readily imagined. Upon hearing their cries, the prisoner raised his head. His eyes gleamed with sudden hope, and, without too thoroughly comprehending what was taking place, he stretched out his hands to his unexpected deliverers.

"He is alive!" exclaimed Ferguson. "God be praised! The savages have got a fine scare, and we shall save him! Are you ready, friends?"

"Ready, doctor, at the word."

"Joe, shut off the cylinder!"

The doctor's order was executed. An almost imperceptible breath of air impelled the balloon directly over the prisoner, at the same time that it gently lowered with the contraction of the gas. For about ten minutes it remained floating in the midst of luminous waves, for Ferguson continued to flash right down upon the throng his glowing sheaf of rays, which, here and there, marked out swift and vivid sheets of light.