Modern History Sourcebook:
Benjamin Franklin:
Experiments with Balloons, 1783
Although the Scientific Revolution was advanced most signally
by a number of profound insights, it was the expansion of a "scientific
mentality" which made it so culturally important. Here the
famous American jack-of-all trade Benjamin Franklin (17061790)
discusses in letters his experiments. . After he left Boston in
1723, he moved to Philadelphia, which he helped establish as one
the centers of the Enlightenment in the American colonies. His
work as an inventor (for instance his invention of a stove in
1742) and his theory on the identity of lightning and electricity,
made him among the most famous of Americans in Europe.
These two letters, were written from France in 1783, at a time
when Franklin was serving with the American diplomatic mission.
TO SIR JOSEPH BANKS
Passy, Dec. 1, 1783. Dear Sir:-
In mine of yesterday I promised to give you an account of Messrs.
Charles & Robert's experiment, which was to have been made
this day, and at which I intended to be present. Being a little
indisposed, and the air cool, and the ground damp, I declined
going into the garden of the Tuileries,2 where the balloon was
placed, not knowing how long I might be obliged to wait there
before it was ready to depart, and chose to stay in my carriage
near the statue of Louis XV., from whence I could well see it
rise, and have an extensive view of the region of air through
which, as the wind sat, it was likely to pass. The morning was
foggy, but about one o'clock the air became tolerably clear, to
the great satisfaction of the spectators, who were infinite, notice
having been given of the intended experiment several days before
in the papers, so that all Paris was out, either about the Tuileries,
on the quays and bridges, in the fields, the streets, at the windows,
or on the tops of houses, besides the inhabitants of all the towns
and villages of the environs. Never before was a philosophical
experiment so magnificently attended. Some guns were fired to
give notice that the departure of the balloon was near, and a
small one was discharged, which went to an amazing height, there
being but little wind to make it deviate from its perpendicular
course, and at length the sight of it was lost. Means were used,
I am told, to prevent the great balloon's rising so high as might
endanger its bursting. Several bags of sand were taken on board
before the cord that held it down was cut, and the whole weight
being then too much to be lifted, such a quantity was discharged
as to permit its rising slowly. Thus it would sooner arrive at
that region where it would be in equilibrio with the surrounding
air, and by discharging more sand afterwards, it might go higher
if desired. Between one and two o'clock, all eyes were gratified
with seeing it rise majestically from among the trees, and ascend
gradually above the buildings, a most beautiful spectacle. When
it was about two hundred feet high, the brave adventurers held
out and waved a little white pennant, on both sides their car,
to salute the spectators, who returned loud claps of applause.
The wind was very little, so that the object though moving to
the northward, continued long in view; and it was a great while
before the admiring people began to disperse. The persons embarked
were Mr. Charles, professor of experimental philosophy, and a
zealous promoter of that science; and one of the Messieurs Robert,
the very ingenious constructors of the machine. When it arrived
at its height, which I suppose might be three or four hundred
toises, [A toise was a distance of about 2 meters] it appeared
to have only horizontal motion. I had a pocketglass, with
which I followed it, till I lost sight first of the men, then
of the car, and when I last saw the balloon, it appeared no bigger
than a walnut. I write this at seven in the evening. What became
of them is not yet known here. I hope they descended by daylight,
so as to see and avoid falling among trees or on houses, and that
the experiment was completed without any mischievous accident,
which the novelty of it and the want of experience might well
occasion. I am the more anxious for the event, because I am not
well informed of the means provided for letting themselves down,
and the loss of these very ingenious men would not only be a discouragement
to the progress of the art, but be a sensible loss to science
and society.
I shall inclose one of the tickets of admission, on which the
globe was represented, as originally intended, but is altered
by the pen to show its real state when it went off. When the tickets
were engraved the car was to have been hung to the neck of the
globe, as represented by a little drawing I have made in the corner.
I suppose it may have been an apprehension of danger in straining
too much the balloon or tearing the silk, that induced the constructors
to throw a net over it, fixed to a hoop which went round its middle,
and to hang the car to that hoop.
Tuesday morning, December 2d.-I am relieved from my anxiety
by hearing that the adventurers descended well near L'lsle Adam
before sunset. This place is near seven leagues from Paris. Had
the wind blown fresh they might have gone much farther.
If I receive any further particulars of importance, I shall communicate
them hereafter.
With great esteem, I am, dear sir, your most obedient and most
humble servant,
B. FRANKLIN
P.S. Tuesday evening.-Since writing the above I have received
the printed paper and the manuscript containing some particulars
of the experiment, which I enclose. I hear further that the travellers
had perfect command of their carriage, descending as they pleased
by letting some of the inflammable air escape, and rising again
by discharging some sand; that they descended over a field so
low as to talk with the labourers in passing, and mounted again
to pass a hill. The little balloon falling at Vincennes shows
that mounting higher it met with a current of air in a contrary
direction, an observation that may be of use to future aerial
voyagers.
From Nathan G. Coodman, ed. The Ingenious Dr. Franklin, Selected
Scientific Letters of Benjamin Franklin (Philadelphia: University
of Pennsylvania Press, 1931), pp. 99105.
To JAN INGENHOUSZ
Passy,Jan. 16, 1784. Dear Friend,
I have this day received your favor of the 2d inst. Every information
in my power, repecting the balloons, I sent you just before Christmas,
contained in copies of my letters to Sir Joseph Banks. There is
no secret in the affair, and I make no doubt that a person coming
from you would easily obtain a sight of the different balloons
of Montgolfier and Charles, with all the instructions wanted;
and, if you undertake to make one, I think it extremely proper
and necessary to send an ingenious man here for that purpose:
otherwise, for want of attention to some particular circumstance,
or of not being acquainted with it, the experiment might miscarry,
which, in an affair of so much public expectation, would have
bad consequences, draw upon you a great deal of censure, and affect
your reputation. It is a serious thing to draw out from their
affairs all the inhabitants of a great city and its environs,
and a disappointment makes them angry. At Bordeaux lately a person
who pretended to send up a balloon, and had received money from
many people, not being able to make it rise, the populace were
so exasperated that they pulled down his house, and had like to
have killed him.
It appears, as you observe, to be a discovery of great importance,
and what may possibly give a new turn to human affairs. Convincing
sovereigns of the folly of wars may perhaps be one effect of it;
since it will be impracticable for the most potent of them to
guard his dominions. Five thousand balloons, capable of raising
two men each, could not cost more than have ships of the line;
and where is the prince who can afford so to cover his country
with troops for its defence, as that ten thousand men descending
from the clouds might not in many places do an infinite deal of
mischief, before a force could be brought together to repel them?
It is a pity that any national jealousy should, as you imagine
it may, have prevented the English from prosecuting the experiment,
since they are such ingenious mechanicians, that in their hands
it might have made a more rapid progress towards perfection, and
all the utility it is capable of affording.
The balloon of Messrs. Charles and Robert was really filled with
inflamable air. The quantity being great, it was expensive, and
tedious filling, requiring two or three days and nights constant
labour. It had a soupape, [or valve], near the top, which
they could open by pulling a string and thereby let out some air
when they had a mind to descend; and they discharged some of their
ballast of sand when they would rise again. A great deal of air
must have been let out when they landed, so that the loose part
might envelope one of them: yet, the car being lightned by that
one getting out of it, there was enough left to carry up the other
rapidly. They had no fire with them. That is only used in M. Montgolfier's
globe, which is open at bottom, and straw constantly burnt to
keep it up. This kind is sooner and cheaper filled; but must be
much bigger to carry up the same weight; since air rarified by
heat is only twice as light as common air, and inflamable air
is ten times lighter. M. de Morveau, a famous chemist at Dijon,
has found an inflamable air that will cost only a 25th part of
the price of what is made by oil of vitriol [sulphuric acid]
poured on iron filings. They say it is made from sea coal. Its
comparative weight is not mentioned.
Yours most affectionately,
B. FRANKLIN.
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(c)Paul Halsall Aug 1997
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