Jules Verne

“ If my chart be exact, we are going to ascend to an elevation of five thousand feet."
"Shall we often have occasion to reach those far upper belts of the atmosphere?"
"Very seldom: the height of the African mountains appears to be quite moderate compared with that of the European and Asiatic ranges; but, in any case, our good Victoria will find no difficulty in passing over them."
In a very little while, the gas expanded under the action of the heat, and the balloon took a very decided ascensional movement. ”

“ The most abrupt declivity of these mountains confronts the Zanzibar coast, but the western slopes are merely inclined planes. The depressions in the soil are covered with a black, rich loam, on which there is a vigorous vegetation. ”

“ Joe, slipping nimbly down the tree, carefully attached the anchor, and the doctor left his cylinder at work to a certain degree in order to retain sufficient ascensional force in the balloon to keep it in the air. Meanwhile the wind had suddenly died away.
"Now," said Ferguson, "take two guns, friend Dick-- one for yourself and one for Joe--and both of you try to bring back some nice cuts of antelope-meat; they will make us a good dinner."
"Off to the hunt!" exclaimed Kennedy, joyously. ”

“ Barral and Bixio, also ventured into the very lofty regions; but their balloon burst--"
"And they fell?" asked Kennedy, abruptly.
"Certainly they did; but as learned men should always fall--namely, without hurting themselves."
"Well, gentlemen," said Joe, "you may try their fall over again, if you like; but, as for me, who am but a dolt, I prefer keeping at the medium height--neither too far up, nor too low down. It won't do to be too ambitious."
At the height of six thousand feet, the density of the atmosphere has already greatly diminished ”

“ Besides, the dilation of the hydrogen involved no danger, and only three-fourths of the vast capacity of the balloon was filled when the barometer, by a depression of eight inches, announced an elevation of six thousand feet.
"Shall we go this high very long?" asked Joe.
"The atmosphere of the earth has a height of six thousand fathoms," said the doctor; "and, with a very large balloon, one might go far. ”