A Rapid Passage.--Prudent Resolves.--Caravans in Sight.--Incessant Rains.-- Goa.--The Niger.--Golberry, Geoffroy, and Gray.--Mungo Park.--Laing.-- Rene Caillie.--Clapperton.--John and Richard Lander.

The 17th of May passed tranquilly, without any remarkable incident; the desert gained upon them once more; a moderate wind bore the Victoria toward the southwest, and she never swerved to the right or to the left, but her shadow traced a perfectly straight line on the sand.

Before starting, the doctor had prudently renewed his stock of water, having feared that he should not be able to touch ground in these regions, infested as they are by the Aouelim-Minian Touaregs. The plateau, at an elevation of eighteen hundred feet above the level of the sea, sloped down toward the south. Our travellers, having crossed the Aghades route at Murzouk--a route often pressed by the feet of camels--arrived that evening, in the sixteenth degree of north latitude, and four degrees fifty-five minutes east longitude, after having passed over one hundred and eighty miles of a long and monotonous day's journey.

During the day Joe dressed the last pieces of game, which had been only hastily prepared, and he served up for supper a mess of snipe, that were greatly relished. The wind continuing good, the doctor resolved to keep on during the night, the moon, still nearly at the full, illumining it with her radiance. The Victoria ascended to a height of five hundred feet, and, during her nocturnal trip of about sixty miles, the gentle slumbers of an infant would not have been disturbed by her motion.

On Sunday morning, the direction of the wind again changed, and it bore to the northwestward. A few crows were seen sweeping through the air, and, off on the horizon, a flock of vultures which, fortunately, however, kept at a distance.

The sight of these birds led Joe to compliment his master on the idea of having two balloons.

"Where would we be," said he, "with only one balloon? The second balloon is like the life-boat to a ship; in case of wreck we could always take to it and escape."

"You are right, friend Joe," said the doctor, "only that my life-boat gives me some uneasiness. It is not so good as the main craft."

"What do you mean by that, doctor?" asked Kennedy.

"I mean to say that the new Victoria is not so good as the old one. Whether it be that the stuff it is made of is too much worn, or that the heat of the spiral has melted the gutta-percha, I can observe a certain loss of gas. It don't amount to much thus far, but still it is noticeable. We have a tendency to sink, and, in order to keep our elevation, I am compelled to give greater dilation to the hydrogen."

"The deuce!" exclaimed Kennedy with concern; "I see no remedy for that."

"There is none, Dick, and that is why we must hasten our progress, and even avoid night halts."

"Are we still far from the coast?" asked Joe.

"Which coast, my boy? How are we to know whither chance will carry us? All that I can say is, that Timbuctoo is still about four hundred miles to the westward.

"And how long will it take us to get there?"

"Should the wind not carry us too far out of the way, I hope to reach that city by Tuesday evening."

"Then," remarked Joe, pointing to a long file of animals and men winding across the open desert, "we shall arrive there sooner than that caravan."

Ferguson and Kennedy leaned over and saw an immense cavalcade. There were at least one hundred and fifty camels of the kind that, for twelve mutkals of gold, or about twenty-five dollars, go from Timbuctoo to Tafilet with a load of five hundred pounds upon their backs. Each animal had dangling to its tail a bag to receive its excrement, the only fuel on which the caravans can depend when crossing the desert.

These Touareg camels are of the very best race. They can go from three to seven days without drinking, and for two without eating. Their speed surpasses that of the horse, and they obey with intelligence the voice of the khabir, or guide of the caravan. They are known in the country under the name of mehari.

Such were the details given by the doctor while his companions continued to gaze upon that multitude of men, women, and children, advancing on foot and with difficulty over a waste of sand half in motion, and scarcely kept in its place by scanty nettles, withered grass, and stunted bushes that grew upon it. The wind obliterated the marks of their feet almost instantly.

Joe inquired how the Arabs managed to guide themselves across the desert, and come to the few wells scattered far between throughout this vast solitude.

"The Arabs," replied Dr. Ferguson, "are endowed by nature with a wonderful instinct in finding their way. Where a European would be at a loss, they never hesitate for a moment. An insignificant fragment of rock, a pebble, a tuft of grass, a different shade of color in the sand, suffice to guide them with accuracy. During the night they go by the polar star. They never travel more than two miles per hour, and always rest during the noonday heat. You may judge from that how long it takes them to cross Sahara, a desert more than nine hundred miles in breadth."