Seeing Further: The Story of Science, Discovery, and the Genius of the Royal Society - Bill Bryson (2010)

7. RICHARD HOLMES

A NEW AGE OF FLIGHT: JOSEPH BANKS GOES BALLOONING

Richard Holmes, biographer and travel writer, is a Fellow of the British Academy and author of celebrated works on Shelley, Coleridge and young Dr Johnson. His latest book, The Age of Wonder, is an examination of the life and work of the scientists of the Romantic age who laid the foundations of modern science. It was shortlisted for the Samuel Johnson Prize, and won the 2009 Royal Society Prize for Science Books.

NEWTON’S THEORIES IMPRESSED THE INTELLECTUALS, BUT THE MASS APPEAL OF BALLOONING REALLY SPREAD THE IDEA THAT A NEW AGE WAS DAWNING. THE ROYAL SOCIETY MAINTAINED A PROPER SCIENTIFIC SCEPTICISM. BUT AS RICHARD HOLMES REVEALS, ITS PRESIDENT WAS A GOOD DEAL MORE INTRIGUED THAN HE LET ON IN PUBLIC.

BALLOMANIA

On 6 November 1783, the recently elected President of the Royal Society, the botanist Joseph Banks, called a special meeting of the Fellows at their splendid new premises in Somerset House. The subject up for discussion was a controversial one: the extraordinary phenomenon of the French ‘aerostatique Machines’.

Banks had received two long and confidential ‘papers’ from Benjamin Franklin, the American Ambassador in Paris, describing the experiments of the Montgolfier brothers with hot-air balloons; and of Dr Alexander Charles with hydrogen balloons. Franklin prophesied – correctly – that the first manned flight in history was about to occur. A balloon would inevitably ‘carry up a Man’. Pilâtre de Rozier and the Marquis d’Arlandes duly took to the air on 19 November 1783. So what, Franklin wondered mildly, did the British intend to do about it all? 

After the meeting, Banks wrote back thanking Franklin for his ‘Philosophical amusements’, but playing down any notion of Anglo-French competition in balloon technology. Instead he sounded a note of ironic caution. ‘I think I see an inclination in the more respectable parts of the Royal Society to guard against the Ballomania which has prevailed, and not to patronise Balloons merely on account of their rising in the Atmosphere, till some Experiment likely to prove beneficial either to Society or Science, is proposed to be an next to them.’ Banks’s witty coinage – ‘ballomania’ – was destined to float quite as far as the balloons themselves.

It is usually said that the Royal Society subsequently – and wisely – made little attempt to sponsor, fund or even foster rival British balloon experiments. Its Fellows were gently discouraged by Banks, who continued to dismiss ‘ballomania’ as a typically French craze for novelty and display. It was a passing fashion that could have no scientific outcome. Like the exactly contemporary French craze for Mesmerism (also reported by Franklin), it would soon dissipate and be utterly forgotten.

Certainly, all the early balloon ascents made in England in the following months, unlike those in France, were privately funded through commercial exhibitions or subscriptions. There was no official sponsorship from the Society or the Crown, or from any university or public institution – unless one counts the glamorous Georgiana, Duchess of Devonshire as a public institution. Moreover nearly all the successful British ascents were in fact made by foreign aeronauts and showmen, such as the young Neapolitan Vincenzo Lunardi, the Italian Count Francesco Zambeccari, the Frenchman Jean-Pierre Blanchard and the American Dr John Jeffries.

Banks’ views appeared to express a mixture of sensible scientific scepticism, combined with a somewhat aloof disapproval of French excitability. Patriotically, he always insisted that the science of ballooning had been originated by the British, in the ‘inflammable air’ experiments of Henry Cavendish, Joseph Black and Joseph Priestley. Only the French, he joked, would have turned Cavendish’s elegant soap bubbles of hydrogen into the seventy-foot monster of ‘Montgolfier’s flying Medusa’ (appropriately powered by hot or ‘rarefied’ French air).

The ballomania which ensued over the next two years is often remembered in terms of the sudden rage for balloon fashion accessories which seized Paris (and to some extent London). This might now be termed Montfgolfier merchandising. Both the Musée de l’Air at Le Bourget and the Blythe House section of the Science Museum, London, are crammed with a wild selection of these astonishing, and sometimes rather beautiful, artefacts. They include popular prints, paintings, satirical cartoons, fans, snuffboxes, teapots, chinaware, lampshades, tobacco pipes, ladies’ garters, milk jugs, hair clips, coat buttons, desk handles, parasols, pen-holders, and even (at Le Bourget) a ceramic toilet bowl with ‘Bon Voyage’ glazed on the interior.

But the element that Banks truly distrusted in ballomania was its demagogic potential. His secretary, Dr Charles Blagden FRS, a chemist who also worked for Cavendish and travelled frequently in France, perhaps encouraged these misgivings. So in August 1783 he informed Banks: ‘all Paris is in an uproar about the flying machines’. In October he noted: ‘It appears that the enthusiasm, I almost said madness, which prevailed in Paris on the subject of balloons, has taken a turn more characteristic of the [French] nation, and is converted into a most violent party spirit. Ridicule and invective, verse and prose, are employed without mercy on this occasion.’

Blagden enjoyed passing on comic or frankly scabrous material. He obtained a French satirical pamphlet purporting to recount ‘the supposed conversations between the three animals which went up in [Montgolfier’s] globe’ at Versailles. The cockerel (symbol of France) seemed somewhat subdued on its return to earth, and ‘all the animals’ complained about the novel experience of air-sickness.

Blagden also gleefully reported the open war in Paris between supporters of hot air and those of hydrogen, quoting an unacademic phrase of Dr Alexander Charles: ‘La belle cacade que Faujas et Montgolfier ont fait.’ He then added primly: ‘I know no decent English translation of this term [cacade].’ Banks (a product of Eton and Oxford) knew of course that cacade meant a heap of shit. Blagden concluded sententiously: ‘Every thing that occurs relative to this business makes me rejoice that during all the Heat & Enthusiasm of our Neighbours we retained in this country a true Philosophical Tranquillity.’

A year later, in September 1784, he was happy to pass on the opinion of his friend, the distinguished French chemist Claude Berthollet. ‘Aerostatic globes and Animal Magnetism have, during the whole of this past year, so filled people’s heads in this country that useful research has been utterly neglected.’ Blagden added pointedly that this now expressed the view of ‘the soberer part’ of the French Academy.

French ballooning certainly generated the most powerful outpouring of popular feeling. It also assembled enormous crowds in Paris, full of dangerous utopian dreams and heady aspirations. The kind of eyewitness account of such balloon launches which would have alarmed Banks is well illustrated by Le Tableau de Paris, 1 December 1783: 

The swarm of people was itself an incomparable sight, so varied was it, so vast and so changing. Two hundred thousand men, lifting their hands in wonder, admiring, glad, astonished; some in tears for the intrepid philosophers should they come to harm; some on their knees overcome with emotion; but all following the aeronauts in spirit, while these latter, unmoved, saluted, dipping their flags above our heads. What with the novelty, the dignity of the experiment; the unclouded sun, welcoming as it were the travellers to his own element; the attitude of the two men themselves sailing into the blue, while below their fellow-citizens prayed and feared for their safety; and lastly the balloon itself, superb in the sunlight, soaring aloft like a planet, or the chariot of some weather-god! It was a moment which can never be repeated, the most astounding achievement the science of physics has yet given to the world.

Yet such wild enthusiasm could strongly appeal to a British physician and inventor like Dr Erasmus Darwin. Though Darwin was a Fellow of the Royal Society (elected in 1761), he was also part of a radical and nonconformist network of provincial philosophers, and a leading light of the Lunar Society based in Birmingham and Derby. Moreover he was a poet.

Darwin saw the Montgolfiers as the pioneers of a new age, and was untroubled by Banks’ scientific reservations or patriotic anxieties. He celebrated the Montgolfiers’ early flights in a long, ecstatic passage from his poem The Loves of the Plants (eventually published in 1789). A botanical description of a flying thistle-seed from Canto 2, ‘Air’, was suddenly transformed into an image of an airborne French balloon:

…Soon the shoreless air the intrepid Gaul
Launch’d the vast concave of his buoyant ball,
Journeying on high, the silken castle glides
Bright as a meteor through the azure tides;
O’er towns, and towers, and temples wins its way,
Or mounts sublime, and gilds the vault of day …

Darwin presents the Montgolfier balloon’s ascent first as seen from below, as the watching crowd gaze upwards, torn between rapture and terror:

Silent with upturn’d eye unbreathing crowds
Pursue the floating wonder to the clouds;
And flush’d with transport, or benumb’d with fear
Watch, as it rises, the diminish’d sphere.
Now less and less – and now a speck is seen –
And now the fleeting rack obtrudes between!

Then Darwin ascends to the imagined view from above, looking out from the aeronaut’s basket, at the very edge of the stratosphere. The aeronaut gazes down upon the Earth, but also upwards at the stars revealed above him. He observes the clouds and the weather systems. He even sees (like the future astronauts) the curvature of the planet itself, in the blue horizon-line of the ocean:

The calm Philosopher in ether sails,
Views broader stars and breathes in purer gales;
Sees like a map in many a waving line,
Round earth’s blue plains her lucid waters shine;
Sees at his feet the forky lightning glow
And hears innocuous thunder roar below …

Finally, in a quite extraordinary passage, Darwin sends the balloon on a fantasy voyage right through the solar system. Here science is frankly abandoned for science fiction. ‘Rise, great Montgolfier! Urge thy venturous flight / High o’er the moon’s pale ice-reflected light.’ He sails past ‘the red eye’ of Mars, floats round Jupiter, and surges beyond Saturn with its ‘crystal rings’ and Herschel’s newly discovered ‘Georgian’ planet of Uranus. He elevates magnificently through the Milky Way, and the glittering constellations of the zodiac. He becomes a new North star, ‘to blaze eternal round the wondering pole’, a beckoning light to all future space ‘mariners’. (The Loves of the Plants, 1789, Canto 2, lines 27–66.)

British journalists, though more sceptical than poets, were not entirely immune to such fantasy journeys either. They also saw the immense possibilities of balloon flight, and responded to the first reports of the French experiments. A long article on ballooning in the Monthly Review at the end of 1783 concluded:

We found our imaginations warmed by the gigantic idea of our penetrating some day into the wildest and most inhospitable regions of Africa, Arabia, and America, of our crossing chains of mountains hitherto impervious, and ascending their loftiest summits, of our reaching either of the two poles and in short, of our extending our dominion over the creation beyond any thing which we now have conception.

REPORTS

It was exactly this kind of ballomania and unscientific speculation that Joseph Banks is reputed to have dismissed out of hand. Yet the recent publication of Banks’ Scientific Correspondence,1 and a re-examination of the Royal Society archives suggests a more complex and intriguing state of affairs.

First, it turns out that no fewer than fifty letters on the subject of ballooning were exchanged between Banks and his scientific correspondents between 1783 and 1786. Not only Banks himself, but several other Fellows of the Royal Society (besides Darwin) were evidently fascinated by ballooning, and became far more closely involved than has been previously assumed.

It is also clear that the latest balloon news, including extensive cuttings from the French newspapers, and many ‘a parcel of pamphlets and journals’, was regularly supplied to Banks not only by Charles Blagden, but also by Banks’ personal assistant and librarian at Soho Square, the Swedish botanist Jonas Dryander.

This began in September 1783 when Dryander excitedly passed on a package from Paris: ‘Journal de Paris from August to September 17 is just come. I have only had time to turn over some of the last numbers to hunt for information about the great aerostatique experiment. I’ll copy here the description of the machine…’

Banks continued to receive such detailed reports of all the French balloon ascents throughout the rest of 1783 and 1784. He was informed that the French Academy of Sciences, under his opposite number the Marquis de Condorcet, had appointed an official commission to investigate ‘aerostation’, and were funding further ascents by Pilâtre de Rozier. He also received various communications from Barthélemy Faujas de Saint-Fond, a geologist and official from the Jardin du Roi, who had set himself up as a commercial promoter of ballooning in France. Saint-Fond published one of the earliest books on the subject, Descriptions des Experiences des Machines Aerostatiques de MM Montgolfier; Banks had obtained his own copy by the end of November 1783. 

Apart from Blagden, Dryander and Saint-Fond, Banks’ most important source of balloon information was Benjamin Franklin, by then in his seventies and wise in the ways of both men and machines. It has not been appreciated how significant this contact was. Franklin’s ‘two papers’, submitted to the Society in November 1783, were in reality just part of an extensive exchange of confidential letters and ballooning documents between him and Banks, amounting to no fewer than sixteen items, which continued virtually unbroken from July 1783 to April 1785.

Banks’ fascination with ballooning is expressed much more openly to Franklin than to anyone else. In September 1783 he wrote: ‘Most agreeable are the hopes you give me … I consider the present day which has opened a Road in the Air, as an Epoch … the more immediate Effect it will have upon the concerns of mankind, [is] greater than anything since the invention of Shipping …’

It was to Franklin, rather than to Blagden, that Banks wrote so warmly on 28 November 1783, immediately after the Montgolfiers’ first manned flight.

The Experiment now becomes interesting in no small degree. I laughed when Balloons of scarce more importance than soap bubbles occupied the attention of France. But when men can with safety pass, and do pass, more than 5 miles in the first Experiment I begin to fancy that I espy the hand of the Master in the education of the Infant Knowledge, who so speedily attains such a degree of maturity …

If not a ‘ballomaniac’, Franklin was certainly in favour of balloons. He had interviewed Joseph Montgolfier and the Marquis d’Arlandes at the American Embassy, the evening after that first manned flight. He had also witnessed Dr Charles’s first ascent by hydrogen balloon from the Tuilleries on 1 December, and sent Banks a most eloquent account. ‘All Paris was out, either about the Tuilleries, on the quays and bridges, in the fields, the streets, at the windows, or on the tops of houses …’

It was after this flight that Franklin was reported to have made his famous remark, when asked what was the use of a balloon: ‘I replied – what’s the use of a newborn baby?’ Perhaps he was inspired by Banks’ earlier reference to ‘the Infant Knowledge’.

Banks again wrote enthusiastically to Franklin on 9 December:

The new Art of Flying … makes such rapid advances in the country you now inhabit … Charles’s Experiment seems decisive, and must be performed here in its full extent. I have hitherto been of the Opinion that it is unwise to struggle for the honour of an invention that is about to be Effected. Practical flying we must allow to our rivals, Theoretical flying we claim ourselves … When our Friends on your side of the water are cooled a little … they shall see that we will visit the repositories of the Stars and Meteors.

The question now became, what were the realistic applications of ‘Practical flying’, as opposed to theories and fantasies?

PRACTICAL FLYING

Indeed it was not at first clear, either to the Royal Society or the French Academy of Sciences, what the true purpose or possibilities of ballooning really were. In fact ‘flight’ was itself a novel and surprisingly unexplored concept, despite an extensive literary tradition from Icarus and Pegasus onwards. What, in practice, could balloons actually do for mankind, except provide a hazardous journey interspersed with fine aerial ‘Prospects’?2

According to Saint-Fond they might, for example, provide observation platforms: for military reconnaissance, for sailors at sea, for chemists analysing the Earth’s upper atmosphere, or for astronomers with their telescopes. It is notable that most of these applications were based on the notion of a tethered balloon. In fact many of the Montgolfiers’ early experiments were made with tethered aerostats, held to the ground by various ingenious forms of harness, guy ropes or winches.

Despite his poetical effusions, Erasmus Darwin’s first practical idea of balloon-power was paradoxically that of shifting payloads along the ground. He suggested to his friend Richard Edgeworth that a small hydrogen balloon might be tethered to an adapted garden wheel-barrow, and used for transporting heavy loads of garden manure up the steep hills of his Irish estate. This convenient aerial skip would allow one man to shift ten times his normal weight. Indeed it might revolutionise manual labour.

Similarly, Banks himself had the initial idea that balloons could increase the effectiveness of earth-bound transport, by adding to its conventional horsepower. He saw the balloon as ‘a counterpoise to Absolute Gravity’: that is, as a flotation device to be attached to traditional forms of coach or cart, making them easier to move over the ground. So ‘a broad-wheeled wagon’ normally requiring eight horses to pull it, might only need two horses with a Montgolfier attached. This aptly suggests how difficult it was, even for a trained scientific mind like Banks’, to imagine the true possibilities of flight in these early days.

Franklin, ‘the old fox’ as Blagden called him, was quick to suggest various menacing military applications, perhaps deliberately intended to fix Banks’ attention. ‘Five thousand balloons capable of raising two men each’ could easily transport an effective invasion army often thousand marines across the Channel, in the course of a single morning. The only question was, Franklin implied, which direction would the wind be blowing from?

His other speculations were more light-hearted. What about a ‘running Footman’? Such a man might be suspended under a small hydrogen balloon, so his body weight was reduced to ‘perhaps 8 or 10 Pounds’, and thus made capable of running in a straight line in leaps and bounds ‘across Countries as fast as the Wind, and over Hedges, Ditches & even Water…’ Or there was the balloon ‘Elbow Chair’, placed in a beauty spot, and winching the picturesque spectator ‘a Mile high for a Guinea’ to see the view. Then there was Franklin’s patent balloon icebox. ‘People will keep such Globes anchored in the Air, to which by Pullies they may draw up Game to be preserved in the Cool, & Water to be frozen when Ice is wanted.’ This contraption would surely have appealed to that twentieth-century illustrator Heath Robinson.

Many other ingenious suggestions were made, including the use of balloons as buoyancy tanks for ships, as aerial river-ferries, and for air mail between towns. The latter merely required that the recipients were always precisely downwind of the sender. Indeed, Erasmus Darwin attempted to pioneer balloon-post by sending a Christmas letter in December 1783, attached to a small hydrogen balloon. It was meant to fly northwards carrying seasonal greetings from the Philosophical Society in Derby to Matthew Boulton’s garden in Birmingham. In the event it overshot by fifteen miles when ‘the wicked wind carried it to Sir Edward Littleton’s’.3

Thomas Martyn, a Professor of Botany at Cambridge, published an illustrated pamphlet appealing directly to the Royal Society, Hints of Important Uses for Aerostatic Globes, 1784. Martyn’s big idea was high-speed visual communications by tethered balloon. He urged the use of balloons as signal platforms, invaluable for directing armies on land or fleets at sea. A day-time system of flag semaphore could be replaced by fireworks at night – a rather more problematic suggestion. ‘These Experiments … might be beyond measure enlarged and extended under the direction of a public body, such as our Royal Society.’

Finally even Professor Martyn succumbed to aerostatic fantasy, by fixing an astonishing frontispiece to his pamphlet. It showed a huge, beautiful dream-balloon soaring magnificently amidst the clouds, carrying beneath it a solid, wooden ocean-going ‘air-ship’, with square-rigged sails, large sea-going rudder and elegant anchor on a chain, evidently ready to circumnavigate the entire globe.

NAVIGATION

The great emerging scientific question became this: could an aerostat be navigated? Was it truly an ‘air-ship’? Could a balloon be steered against the prevailing air current, to a previously chosen destination? Could it ever, quite simply, provide a sure method of getting from A to B? Throughout 1784 Banks closely followed the British balloon flights of Lunardi and Blanchard with this navigation question in mind. Several distinguished Fellows of the Royal Society were sent to observe them. Blagden and Cavendish, together with the astronomers Herschel and Aubert, stationed themselves at various rooftop vantage points in London, equipped with telescopes and quadrants. They carefully sent back their data to Banks, and made a special point of observing the effects of wings, oars and rudders on the balloon’s horizontal flight-path. Could it be diverted against or across the wind, however marginally? Lunardi favoured simple wooden oars for this task, while Blanchard proclaimed his faith in silken wings, cotton rudders and a complex propeller-type device known as a moulinette (‘a sort of ventilator that could be turned by means of a handle’). Despite their repeated claims, none of this equipment produced the least observable effect.

These negative observations were significant, because aeronauts in France had been claiming that they could produce a slightly diverted flight-path across the line of the wind, using sails and rudders. During an impressive 150-mile flight made from Paris to Artois on 19 September 1784, the Roberts brothers, who had helped design Dr Charles’ original balloon, stated with pseudo-scientific precision that they had achieved a ‘deflection of 22 degrees’, and ‘might have obtained 80 degrees’. This, they argued, was almost as efficient as a close-hauled sailing ship moving through the comparable medium of water. Banks now had reason to believe that they were deluded.

The one scientific instrument which proved effective in balloon navigation was the mercury barometer. It was already established that air pressure dropped with an increase in altitude. In some sense, not entirely understood, the air got ‘thinner’ the higher one went. So as a balloon rose, an onboard barometer would give a steadily lower reading; and conversely, as the balloon descended, the barometric reading would rise. So an appropriately calibrated barometer (with an adjustable scale set at zero immediately before launching) could act as an altimeter, indicating a balloon’s changing height above the ground.

Banks was therefore particularly scathing when he learned that Lunardi had forgotten to take a barometer on his first historic ascent in September 1784, and had pretended to calculate his maximum altitude from the length of the icicles formed on the lower edge of the balloon canopy. He concluded that the pilot was a brilliant charlatan. Banks feared that Lunardi, having entranced the fashionable and susceptible Duchess of Devonshire, would go on to ensnare the gullible Prince of Wales, and even King George III (already rather less than stable) with his ‘balloon madness’.

But there was an alternative to Lunardi: the Frenchman Jean-Pierre Blanchard. In the autumn of 1784, two Fellows of the Royal Society decided to purchase private passages aboard Blanchard’s hydrogen balloon, making proper observations and taking appropriate equipment with them. The first was John Sheldon, Professor of Anatomy at the Royal Academy, who flew from Chelsea in October 1784.

Despite much anticipation, Sheldon’s flight was largely abortive from a scientific point of view. ‘The balloon was so loaded at first,’ recorded Blagden dryly, ‘that it fell down in a neighbour’s garden.’ Alarmed by the whole experience, Sheldon broke his barometer shortly before take-off, while Blanchard threw overboard the rest of his equipment immediately after. Blanchard mercifully off-loaded the terrified Sheldon at Sunbury, in Middlesex. He then claimed that he had successfully navigated with his wings and rudder some seventy-five miles into Hampshire.

But the first half-hour of the ascent was observed by Blagden and Cavendish from the roof of a house at Putney Heath ‘with instruments’, triangulating their observations with another observer from a house in Earls Court. Their meticulous calculations showed that the balloon ‘floated along with the wind uniformly and regularly, seeming to pay no regard to the operation of the machinery they had taken up’. There was still no indication that a balloon could be navigated.

Blagden estimated that Sheldon had spent £500 on the ascent, and concluded that he had ‘made himself so ridiculous in this business, as to reflect little credit on the Royal Society’. Banks noted, with perhaps pardonable ambiguity, that ‘Mr Sheldon and Mr Blanchard have probably fallen out, as I have not heard a word from them for some time.’

The next philosopher to purchase a flight with Blanchard was the American physician Dr John Jeffries, in November 1784, ascending from Grosvenor Square. In fact, Jeffries was not yet a Fellow of the Royal Society, but hoped to be elected on the strength of his ballooning experiments. Accordingly, he carefully prepared a suite of scientific instruments to take with him: a mercury barometer, a thermometer, a hygrometer and an electrometer, to measure the much-feared electrical charges in clouds. In addition he packed maps, a compass and special note-making equipment. He also strapped aboard special air flasks, to sample the upper atmosphere at different altitudes, which he promised to give to Cavendish for analysis.

Jeffries drew up a memorandum for the Royal Society before they left, stating the main scientific objectives of the ascents, to be achieved by ‘a variety of experiments’ and ‘not for mere amusement’. He was quite precise:

Four points need to be more clearly determined. First, the power of ascending or descending at pleasure, while suspended or floating in the air. Secondly, the effect which oars or wings might be made to produce towards this purpose, and in directing the course of the Balloon. Thirdly, the state and temperature of the atmosphere at different heights above the earth. And fourthly, by observing the varying course of the currents of air, or winds, at certain elevations, to throw some new light on the theory of winds in general.

On this trip, going across the Thames into Kent, Jeffries made the first truly scientific record of a balloon ascent. He meticulously recorded a mass of data – height, direction, air temperature, electrical charges, appearance of clouds, horizon line – at regular time intervals. One of the details which emerged was a ‘profile’ of the characteristic flight-path of a hydrogen balloon: not a single smooth parabola, as had been supposed, but a series of looping ascents and descents, as the balloon moved above and below its ‘equilibrium point’. It was also clear to Jeffries that wind directions often changed at different altitudes. But on the crucial question of navigation, Jeffries could observe no controlled alteration of flight-path, for all Blanchard’s ‘heroic’ rowing and flapping and spinning.

Jeffries went on to take part in the most significant of all the early balloon ascents in Britain, the first crossing of the English Channel with Blanchard on 5 January 1785. He wrote an outstanding account, which exists in at least three versions. The first was sent as a private letter to Banks from Paris shortly after the flight on 13 January 1785, the second as a formal paper published by the Royal Society in the Philosophical Transactions for January 1786, and the third as a retrospective diary.

Despite its apparent triumph, both sporting and diplomatic, the main scientific significance of this flight was that it proved conclusively that a balloon was not navigable, either over land or sea. As Jeffries expressed it privately in his diary, he could only ‘thank God’ and a favourable wind for his survival. He never flew again.

By the end of 1785, Banks too was rapidly losing interest in ballooning. His correspondence with Franklin tailed off into a courteous exchange of medals and compliments. His doubts could be summed up succinctly: balloons were not navigable, and – as he had originally thought – they should be left to the French. Yet at the last Banks may have encouraged a book by a younger Fellow of the Royal Society that would inspire a new generation of aeronauts.

RETROSPECTIVE

In 1785 Tiberius Cavallo FRS published A Treatise on the History and Practice of Aerostation. Cavallo was a brilliant Italian physicist who had moved to London at the age of twenty-two, and had already written extensively on magnetism and electrical phenomena. Elected a Fellow in 1779, he quickly turned his attention to ballooning. He had some claims to be one of the first to inflate soap bubbles with hydrogen as early as 1782. Although a handsome portrait is held by the National Portrait Gallery in London, he is now largely and unjustly forgotten. Yet his study emerges as the most authoritative early treatise on the subject, either in English or French. The copy of Cavallo’s book held by the British Library is personally inscribed ‘To Sir Joseph Banks from the Author’ – in firm, black, racy ink. 

Cavallo adopted a considered and even sceptical tone, well calculated to appeal to Banks. Of his fellow-countryman Lunardi’s historic flight he noted:

Besides the Romantic observations which might be naturally suggested by the Prospect seen from that elevated situation, and by the agreeable calm he felt after the fatigue, the anxiety, and the accomplishment of his Experiment, Mr Lunardi seems to have made no particular philosophical observation, or such as may either tend to improve the subject of aerostation, or to throw light on any operation in Nature.

He analysed and dismissed most claims to navigate balloons, except by the use of different air currents at different altitudes. He emphasised the aeronaut’s vulnerability to unpredictable atmospheric phenomena, such as downdraughts, lightning strikes and ice formation. He deliberately included the alarming account of those who survived when a French balloon was caught in a thunderstorm, during an ascent from St Cloud in July 1784, and dragged helplessly upwards by a thermal:

Three minutes after ascending, the balloon was lost in the clouds, and the aerial voyagers lost sight of the earth, being involved in dense vapour. Here an unusual agitation of the air, somewhat like a whirlwind, in a moment turned the machine three times from the right to the left. The violent shocks, which they suffered prevented their using any of the means proposed for the direction of the balloon, and they even tore away the silk stuff of which the helm was made. Never, said they, a more dreadful scene presented itself to any eye, than that in which they were involved. A unbounded ocean of shapeless clouds rolled one upon another beneath, and seemed to forbid their return to earth, which was still invisible. The agitation of the balloon became greater every moment …

Yet for all this, Cavallo was a passionate balloon enthusiast. He recorded and analysed all the significant flights, both French and English, made from the Montgolfiers’ first balloon at Annonay in June 1783 to Blanchard and Jeffries’ crossing of the Channel in January 1785. He distinguished carefully between hot-air and hydrogen balloons, and their quite different flight characteristics. He looked in detail at methods of preparing hydrogen gas, noting that Priestley had come up with one that used steam rather than sulphuric acid. He also examined the different ways of constructing balloon canopies from rubber (‘cauchouc’), waxed silk, varnished linen and taffeta.

In a longer perspective, he stressed the astonishing speed of aerial travel over the ground – ‘often between 40 and 50 miles per hour’ – combined with its incredible ‘stillness and tranquillity’ in most normal conditions. This he thought must eventually revolutionise transport and communications, even if the moment had not yet arrived. He pointed out that in achieving altitudes of over two miles, balloons opened a whole new dimension to mankind’s observations of the Earth beneath. Man’s growing impact on the surface of the planet became visible from the air for the first time, as did the vast tracts of the Earth – mountains, forests, deserts – yet to be traversed. Above all he stressed that the full potential of flight had not yet been remotely explored.

Cavallo considered the whole range of possible balloon applications. But he finally and presciently championed its relevance to the infant science of meteorology:

The philosophical uses to which these machines may be subservient are numerous indeed; and it may be sufficient to say, that hardly anything of what passes in the atmosphere is known with precision, and that principally for want of a method of ascending into the atmosphere. The formation of rain, of thunder-storms, of vapours, hail, snow and meteors in general, require to be attentively examined and ascertained.

The action of the barometer, the refraction and temperature of air in various regions, the descent of bodies, the propagation of sound etc are subjects which all require a long series of observations and experiments, the performance of which could never have been properly expected, before the discovery of these machines. We may therefore conclude with a wish that the learned, and the encouragers of useful knowledge, may unanimously concur in endeavouring to promote the subject of aerostation, and to render it useful as possible to mankind.

It was largely due to Cavallo’s book that, a decade later, ballooning received a signal acknowledgment and consecration. The third edition of the hugely influential Encyclopaedia Britannica, published in 1797, for the first time recognised the existence of ‘Aerostation’. It described it with all due formality as ‘a science newly introduced to the Encyclopaedia’, and gave it a comprehensive article of fourteen pages. This included two full spreads of diagrammatic illustrations, showing every known kind of aerostats that would actually fly. Almost all the material was drawn, unacknowledged, from Tiberius Cavallo.

The editors of the great Encyclopaedia made one symbolic gesture. They placed as the frontispiece to the opening volume of the new edition a prophetic engraving. It showed a traditional gathering of ‘natural philosophers’ in a Roman forum, arrayed in classical togas and surrounded by pillared Doric temples. (Could they have intended a sly reference to the Royal Society?) They then introduced one striking anachronism. High overhead, a hydrogen balloon (complete with wings) sails imperiously into some unknown future.

Such prophetic dreams would soon be taken up by a new generation of British aeronauts, such as James Sadler and Charles Green. But as for Sir Joseph Banks PRS, now perhaps made more earth-bound by his knighthood, aerostation virtually disappears from his letters after 1790. When in January 1800 he received a charming inquiry from Ireland suggesting a scheme to build a balloon railway beneath a ‘mile-long covered gallery’ at Greenwich, he replied with barely a sigh: ‘The Royal Society have no Funds destined for the Execution of Projects so Expensive as yours must be; nor indeed have they in any one instance interfered in the business of Aerostation.’

1 See the wonderful new edition, The Scientific Correspondence of Joseph Banks 1765–1820, edited by Neil Chambers, 6 vols (London, Pickering & Chatto Ltd, 2007). Further sources are given in my bibliography on page 486.

2 The idea that the ‘Prospect’ itself – the free ascent, the magnificent views, the whole ‘aerial experience’ – was the real point of ballooning, only truly arrived with the sporting, propane-powered hot-air balloons of the late twentieth century. However, one early pioneer of this existential attitude was Thomas Baldwin, whose remarkable Aeropaedia (1786) was an entire book dedicated to a single flight, made from Chester on 8 September 1785. It contained the first ever paintings of the view from a balloon-basket; an analytic diagram of the corkscrew flight path projected over a land map; and a whole chapter simply given up to describing the astonishing colours and structures of cloud-formations. One typical observation reads: ‘The river Dee appeared of a red colour; the city [Chester] very diminutive; and the town [Warrington] entirely blue. The whole appeared a perfect plane, the highest buildings having no apparent height, but reduced all to the same level, and the whole terrestrial prospect appeared like a coloured map.’ [p. 204].

3 The supremely impractical suggestion of balloon mail was to be strangely vindicated by the French some ninety years later. During the Prussian siege of Paris in 1870–71, no fewer than sixty-six hydrogen balloons, each carrying 125 kilos of domestic mail and government despatches, sailed successfully over the Prussian lines, landing as far afield as unoccupied Brittany, whereupon the mail was rapidly distributed by horse across the nation. The first balloon, the Neptune, carried a letter from the photographer Felix Nadar to The Times. Subsequent balloons, with that touch of French genius, teased the Prussians by having patriotic names emblazoned on their canopies in huge letters – the Victor Hugo, the George Sand, the Armand Barbès.