Seeing Further (19 page)

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’.
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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.

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:

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.

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:

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: