Read Online Five Weeks in a Balloon by Jules Verne - Free Book Online
Authors: Jules Verne
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much."
"Useless, my boy!" replied the doctor. "You may
eat as much as you like, and here's half-a-crown to buy
you the ballast."
CHAPTER SEVENTH.
Geometrical Details.—Calculation of the Capacity of the Balloon.—The
Double Receptacle.—The Covering.—The Car.—The Mysterious Apparatus.
—The Provisions and Stores.—The Final Summing up.
Dr. Ferguson had long been engaged upon the details
of his expedition. It is easy to comprehend that the balloon
—that marvellous vehicle which was to convey him
through the air—was the constant object of his solicitude.
At the outset, in order not to give the balloon too
ponderous dimensions, he had decided to fill it with
hydrogen gas, which is fourteen and a half times lighter
than common air. The production of this gas is easy,
and it has given the greatest satisfaction hitherto in
aerostatic experiments.
The doctor, according to very accurate calculations,
found that, including the articles indispensable to his
journey and his apparatus, he should have to carry a weight
of 4,000 pounds; therefore he had to find out what would
be the ascensional force of a balloon capable of raising such
a weight, and, consequently, what would be its capacity.
A weight of four thousand pounds is represented by
a displacement of the air amounting to forty-four thousand
eight hundred and forty-seven cubic feet; or, in other
words, forty-four thousand eight hundred and forty-seven
cubic feet of air weigh about four thousand pounds.
By giving the balloon these cubic dimensions, and filling
it with hydrogen gas, instead of common air—the former
being fourteen and a half times lighter and weighing
therefore only two hundred and seventy-six pounds—a
difference of three thousand seven hundred and twenty-four
pounds in equilibrium is produced; and it is this
difference between the weight of the gas contained in the
balloon and the weight of the surrounding atmosphere
that constitutes the ascensional force of the former.
However, were the forty-four thousand eight hundred
and forty-seven cubic feet of gas of which we speak, all
introduced into the balloon, it would be entirely filled;
but that would not do, because, as the balloon continued
to mount into the more rarefied layers of the atmosphere,
the gas within would dilate, and soon burst the cover
containing it. Balloons, then, are usually only two-thirds
filled.
But the doctor, in carrying out a project known only
to himself, resolved to fill his balloon only one-half; and,
since he had to carry forty-four thousand eight hundred
and forty-seven cubic feet of gas, to give his balloon
nearly double capacity he arranged it in that elongated,
oval shape which has come to be preferred. The horizontal
diameter was fifty feet, and the vertical diameter
seventy-five feet. He thus obtained a spheroid, the
capacity of which amounted, in round numbers, to ninety
thousand cubic feet.
Could Dr. Ferguson have used two balloons, his chances
of success would have been increased; for, should one
burst in the air, he could, by throwing out ballast, keep
himself up with the other. But the management of two
balloons would, necessarily, be very difficult, in view of
the problem how to keep them both at an equal ascensional force.
After having pondered the matter carefully, Dr. Ferguson,
by an ingenious arrangement, combined the advantages of
two balloons, without incurring their inconveniences. He
constructed two of different sizes, and inclosed the
smaller in the larger one. His external balloon, which
had the dimensions given above, contained a less one of
the same shape, which was only forty-five feet in
horizontal, and sixty-eight feet in vertical diameter. The
capacity of this interior balloon was only sixty-seven
thousand cubic feet: it was to float in the fluid surrounding
it. A valve opened from one balloon into the other,
and thus enabled the aeronaut to communicate with both.
This arrangement offered the advantage, that if gas
had to be let off,
"Useless, my boy!" replied the doctor. "You may
eat as much as you like, and here's half-a-crown to buy
you the ballast."
CHAPTER SEVENTH.
Geometrical Details.—Calculation of the Capacity of the Balloon.—The
Double Receptacle.—The Covering.—The Car.—The Mysterious Apparatus.
—The Provisions and Stores.—The Final Summing up.
Dr. Ferguson had long been engaged upon the details
of his expedition. It is easy to comprehend that the balloon
—that marvellous vehicle which was to convey him
through the air—was the constant object of his solicitude.
At the outset, in order not to give the balloon too
ponderous dimensions, he had decided to fill it with
hydrogen gas, which is fourteen and a half times lighter
than common air. The production of this gas is easy,
and it has given the greatest satisfaction hitherto in
aerostatic experiments.
The doctor, according to very accurate calculations,
found that, including the articles indispensable to his
journey and his apparatus, he should have to carry a weight
of 4,000 pounds; therefore he had to find out what would
be the ascensional force of a balloon capable of raising such
a weight, and, consequently, what would be its capacity.
A weight of four thousand pounds is represented by
a displacement of the air amounting to forty-four thousand
eight hundred and forty-seven cubic feet; or, in other
words, forty-four thousand eight hundred and forty-seven
cubic feet of air weigh about four thousand pounds.
By giving the balloon these cubic dimensions, and filling
it with hydrogen gas, instead of common air—the former
being fourteen and a half times lighter and weighing
therefore only two hundred and seventy-six pounds—a
difference of three thousand seven hundred and twenty-four
pounds in equilibrium is produced; and it is this
difference between the weight of the gas contained in the
balloon and the weight of the surrounding atmosphere
that constitutes the ascensional force of the former.
However, were the forty-four thousand eight hundred
and forty-seven cubic feet of gas of which we speak, all
introduced into the balloon, it would be entirely filled;
but that would not do, because, as the balloon continued
to mount into the more rarefied layers of the atmosphere,
the gas within would dilate, and soon burst the cover
containing it. Balloons, then, are usually only two-thirds
filled.
But the doctor, in carrying out a project known only
to himself, resolved to fill his balloon only one-half; and,
since he had to carry forty-four thousand eight hundred
and forty-seven cubic feet of gas, to give his balloon
nearly double capacity he arranged it in that elongated,
oval shape which has come to be preferred. The horizontal
diameter was fifty feet, and the vertical diameter
seventy-five feet. He thus obtained a spheroid, the
capacity of which amounted, in round numbers, to ninety
thousand cubic feet.
Could Dr. Ferguson have used two balloons, his chances
of success would have been increased; for, should one
burst in the air, he could, by throwing out ballast, keep
himself up with the other. But the management of two
balloons would, necessarily, be very difficult, in view of
the problem how to keep them both at an equal ascensional force.
After having pondered the matter carefully, Dr. Ferguson,
by an ingenious arrangement, combined the advantages of
two balloons, without incurring their inconveniences. He
constructed two of different sizes, and inclosed the
smaller in the larger one. His external balloon, which
had the dimensions given above, contained a less one of
the same shape, which was only forty-five feet in
horizontal, and sixty-eight feet in vertical diameter. The
capacity of this interior balloon was only sixty-seven
thousand cubic feet: it was to float in the fluid surrounding
it. A valve opened from one balloon into the other,
and thus enabled the aeronaut to communicate with both.
This arrangement offered the advantage, that if gas
had to be let off,
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