What an outsider like Davy had to encounter in the Northumberland mines was described by a local journalist: ‘It would require all the fortitude of nature to refrain from fear, and to examine everything with calmness and precision. The immense depth [sometimes 600 feet], the innumerable windings and the dark solitary wastes of a coalmine are truly astonishing, and create a sensation of horror in the imagination.’72 ♣
Buddle later recalled: After a great deal of conversation with Sir Humphry Davy, and he making himself perfectly acquainted with the nature of our mines, and what was wanted, just as we were parting he looked at me and said, “I think I can do something for you.” Thinking it was too much ever to be achieved, I gave him a look of incredulity; at that moment it was beyond my comprehension. However, smiling, he said, “Do not despair, I think I can do something for you in a very short time.”’73
From the start, Davy approached each stage of his solution with great originality, and also hectic speed. The Accidents Committee had considered that the prevention of explosions was essentially a problem of designing better ventilation for the mineshafts, rather as Davy had already done in Newgate Prison. Buddle wondered if a different kind of gas could be pumped down to neutralise the fire-damp. But Davy quickly grasped that something far more fundamental was required: safe light.
All miners needed to carry lights (candles or oil lamps) to every part of a mine. How could this be done without exploding the lethal firedamp gas, and moreover without living in permanent fear of such an explosion? The solution must be simple, inexpensive, robust and absolutely reliable: a miner’s ‘safe lamp’. Here Davy took his first original step. Instead of starting with the lamp, as every other inventor had done, he started with the gas. The first step was not the technology of the lamp, but a complete scientific analysis of the gas and all its properties. Buddle undertook to send samples of the fire-damp to London as soon as it could be safely gathered and bottled.
Davy went to ground in Durham for over three weeks, and neither Jane nor any friend in London (except Faraday) knew where he was. He visited numerous mines, talked to miners and overseers, silently observing, analysing and reflecting. He borrowed Dr Clanny’s bellows lamp for a day, but was not impressed. Then he suddenly seems to have made up his mind. He hurried back to London, and precipitately took over the Royal Institution laboratory on 9 October 1815, which he was not really authorised to do. He ordered glass and metal apparatus, capable of ‘withstanding an explosion’, from the Institution’s instrument-maker, John Newman, and summoned Michael Faraday to his assistance.74
They remained closeted in the basement laboratory almost without interruption for three months, pursuing a feverish series of experiments and issuing ongoing reports to the Royal Society. Faraday said he was only let out to attend the weekly meetings of the City Philosophical Society. He later modestly recalled: ‘I was a witness in our laboratory to the gradual and beautiful development of the train of thought and experiments which produced the Safety Lamp.’75
Davy first began a minute analysis of the properties of fire-damp, quickly confirming that it was ‘light carburetted hydrogen’ (methane), with unusual combustion characteristics. He discovered that explosions would only occur when methane reached a critical ratio of gas to air (approximately one to eight parts). It then became true explosive firedamp. Once ignited — a mere lick of a candle flame would do this — it produced an accelerated reaction, spreading with an intense flame that rapidly reached a critical temperature and then exploded with extreme violence. He noted that this critical temperature at which the explosion occurred was surprisingly high: much higher, for example, than for that of the hydrogen used in Charlier balloons.
Paradoxically, fire-damp was also capable, under certain conditions, of burning with a cool flame which did not explode. Accordingly, Davy next tried igniting it in various closed containers. If a glass tube was used, it instantly exploded. But when confined to a narrow metal tube, it would only burn with the cool, slow blue flame he had observed in the Apennines. He established that the reason for this was that the surface of the metal tube, if sufficiently narrow (‘less than an eighth of an inch), had the peculiar property of conducting away the heat and continuously cooling the methane flame, thus keeping it below the critical explosion temperature.
With his analysis of the gas complete, Davy turned his attention to the lamp. He began designing the first model of an enclosed, airtight safety lamp, using a sealed glass chimney round the wick, with a system of narrow metal tubes to let in the air at its base. Methane mixed with air would not explode in these tubes. Davy’s hasty sketches were transformed into neat technical drawings by Faraday. The prototypes were then constructed overnight by the Institution’s temperamental engineer, John Newman, at nearby Lisle Street, so that Davy could immediately try them out the next morning in large glass containers filled with fire-damp. After many disappointments from the instrument-maker’, and some spectacular rows, several possible models began to emerge. This trial-and-error process was a new type of teamwork for Davy, which caused some friction. But crucially it allowed him and Faraday to work very rapidly, and on several concepts at once.76
Despite some fearful explosions, Davy already had at least three working prototypes of a ‘Safe Lantern’ ready by the end of October. All of these were sealed lamps, using various forms of metal tubes or ‘fire sieves’ as air inlets. He summarised his researches in a letter to Banks on 27 October, and a week later sent the lamps to the Royal Society, with a detailed scientific paper which was officially read on 9 November. He also copied his summary in a ‘private communication’, not to be released, to Dr Gray at the Safety Committee.77 Not surprisingly, news of at least one prototype was soon leaked to the Newcastle newspapers, which would later lead to confusion about the exact mechanism Davy had discovered, and a bitter priority dispute.
Banks was triumphant. On 30 October he wrote one of his most flamboyant missives to Davy, bubbling with emphatic capital letters, from Revesby Abbey in Lincolnshire. Davy’s ‘brilliant’ discoveries had given him ‘unspeakable Pleasure’, and would exalt the reputation of the Royal Society throughout the ‘Scientific world’. His personal achievement was nothing less than heroic: ‘To have come forward when called upon, because no one else could discover the means of defending Society from a Tremendous Scourge of Humanity; and to have by the application of Enlightened Philosophy found a means of providing a Certain Precautionary Measure [the lamp] effectual to guard Mankind for the future against this alarming & increasing Evil, cannot fail to recommend the Discoverer to much Public Gratitude, & to place the Royal Society in a more Popular Point of View than all the abstruse discoveries beyond the understanding of unlearned People could do. I shall most certainly direct your paper to be read at the very first day of our meeting.’78
But Banks’s congratulations were premature. The lamps with tubes were only relatively safe, as Davy discovered after further trials. Here his true genius as a man of science — his impetuosity, his imagination, his ambition and his seething energy — were demonstrated. Davy would not rest, nor would he let Faraday rest. Obsessively pursuing his researches into December, and largely ignoring Christmas, to Jane’s evident dismay, he remained closeted with his assistant. In late December or early January he made a further technical breakthrough, which he reported to the Royal Society in a hurried but triumphant paper of 11 January 1816.79
What he had discovered was this. Fine-gauge iron mesh would work even better than thin metal tubes in preventing an explosion. Indeed, it replaced the need for an airtight glass chimney (easily broken) entirely. The fine apertures in the mesh or ‘gauze’ provided the equivalent of hundreds of tiny metal cooling tubes (‘784 apertures to the inch). The function of tubes and gauze was ‘analogous’. This application of metal gauze or ‘tissue’ was the key discovery that no other researcher had hit upon.
The methane passed freely through the iron gauze to the naked flame inside the lamp, ignited there and
burnt vividly. ‘The lower part of the flame is green, the middle purple, and the upper part blue.’ But it could not pass back at sufficient temperature to ignite and explode the firedamp outside in the mine. Even when the gauze became red hot, the flame would not pass through it. Moreover, provided the lamp was entirely enclosed in the iron gauze, it did not have to have an airtight glass chimney. It was much less vulnerable, and could be redesigned as a much cheaper and more robust instrument. Davy wrote dramatically of confining ‘this destructive element flame like a bird in a cage’.80 Holding an iron gauze over a Bunsen burner, and observing that, against all expectation, the flame does not pass through it, is now one of the elementary experiments performed in school chemistry classrooms. It is easy to forget how startling this effect is on seeing it for the first time.
The final version of the lamp was wonderfully simple and surprisingly small. It was a standard uninsulated oil lamp, approximately sixteen inches high, with an adjustable cotton wick, enclosed in a tall column or ‘chimney’ of fine iron mesh. Astonishingly, the lamp required no other protection. In later models Davy added various improvements, largely designed to withstand rough use in the mine.
Yet the fundamental notion that flame would not pass through gauze appeared so unlikely, so completely counter-intuitive, that Davy had to lay out the stages of his discovery with absolute clarity, step by step. The result was a new kind of scientific narrative. The uncertainty and false starts of the experimental laboratory disappeared. Faraday’s sketches showed that trial models had originally included a piston-bellows lamp, a spring-valve lamp and a hinged lamp, none of which was subsequently mentioned.81 Instead the account was transformed into a gripping, single-track narrative of progressive, seemingly inevitable, discovery.
In trying my first tube-lamp in an explosive mixture I found that it was safe; but unless the tubes were very short and numerous, the flame could not well be supported … I arrived at the conclusion that a metallic tissue, however thin and fine, of which the apertures filled more space than the cooling surface, so as to be permeable to air and light, offered a perfect barrier to explosion … In plunging a light surrounded by a cylinder of fine wire gauze into an explosive mixture I saw the whole cylinder become quietly and gradually filled with flame, the upper part of it soon appeared red hot; yet no explosion was produced … I immediately made a number of experiments to perfect this invention, which was evidently the one to be adopted … I placed my lighted lamps in a large glass receiver, and by means of a gasometer filled with coal gas, I made the current of air which passed into the lamp more or less explosive, and caused it to change rapidly or slowly at pleasure, so as to produce all possible varieties of inflammable and explosive mixtures: and I found that iron wire-gauze … was safe under all circumstances … and I consequently adopted this material in guarding lamps for the coal mines, where in January 1816, they were immediately adopted, and have long been in general use.82
When he republished the papers, Davy remarked: ‘Every step was furnished by experiment and induction, in which nothing can be said to be owing to accident, and in which the most simple and useful combination arose out of the most complicated circumstances.’83 In this way he insisted on the Baconian method of stage-by-stage, logical scientific induction, while tacitly admitting the existence of ‘complicated’ versions of the lamp which he had tried and rejected.
This refusal to allow anything to chance, ‘accident’ or good fortune was exactly the same as Herschel’s insistence that chance played no part in his discovery of Uranus. Coleridge had taken this up as one of the key philosophical problems associated with science, in an essay provokingly entitled ‘Does Fortune Favour Fools?’, which he republished in The Friend in 1818. Here he described Davy, perhaps mischievously, as ‘the illustrious Father and Founder of Philosophic Alchemy’. But he praised his great discoveries without reservation, and denied that his scientific research could ever have depended on ‘accident’ or ‘luck’. Yet this left him in a philosophical quandary: did that imply that ‘genius’ and ‘inspiration’ had no place in Davy’s science?84
The essay was originally written in 1809, in response to Davy’s work with the voltaic battery. Coleridge argued that Davy’s discoveries always depended on ‘preconcerted mediation … evolved out of his own intellect’, never on external accident. Davy’s scientific method was always conscious, skilful and deliberate, the fruit of deep knowledge and experience. But the essay raised other issues about scientific research. Coleridge’s way of describing the experimental process betrayed a certain uneasiness. Chemical experiments — using fire or electricity — contained a kind of violence. Davy’s aim was ‘to bind down material Nature under the Inquisition of Reason, and force from her, as by torture, unequivocal answers to prepared and preconceived questions’. Coleridge also wondered if scientific laws could ever truly ‘bind down’ all the phenomena of nature. Newtonian laws could define the phases of the moon, for instance, but could they ever define the movements and appearance of clouds?. ‘The number and variety of their effects baffle our powers of calculation: and that the sky is clear or obscured at any particular time, we speak of, in common language, as a matter of accident’.85
5
The Davy Safety Lamp, the greatest public achievement of his career, would soon be in use all over Britain and Europe. The prototype gauze-enclosed lamp (‘the Davy’) was presented to the Royal Society on 25 January 1816, after being successfully tested at Walls End, Hebburn and several other collieries that month.86
John Buddle, who had witnessed the full horror of several earlier explosions at Walls End, and understood the deep, suppressed fears of miners working in shafts 600 or 1,000 feet beneath the surface, never forgot his first trial with the new Davy Lamp. He later gave a verbatim account to a Parliamentary Committee: ‘On the strength of [Davy’s] authority I took this lamp, without hesitation, into an explosive mixture. I first tried it in an explosive mixture on the surface, and then took it into a mine; and to my astonishment and delight, it is impossible for me to express my feelings at the time when I first suspended the lamp in the mine, and saw it red hot; if it had been a monster destroyed, I could not have felt more exultation than I did. I said to those around me, “We have at last subdued this monster!”’87
Davy went up to Northumberland in March to observe the lamps in action in the mines, and to work on refinements. These would include a platinum coil which relit the wick when it was extinguished by pure methane (‘one of the most beautiful and magical experiments in the science of chemistry experiment’, remarked Faraday), tin draught shields, double gauze at the top of the chimney, and a reinforced open iron frame to protect the gauze if the lamp was struck or dropped.
He went down ‘G’ pit at Walls End, spent some two hours beneath the surface, and according to Buddle delivered an impromptu fifteen-minute lecture on using the lamp safely, stressing the need to avoid strong air currents or clouds of coal dust, which could still risk freak explosions. He also pointed out that the state of the flame indicated the presence, and even the strength, of fire-damp in a shaft. His lamp not only caged the flame, it transformed it into a canary.88
During this visit Davy received a deputation from the mine-owners, with a public letter of thanks describing his lamp as ‘a discovery unparalleled in the history of mining’. It was hoped that ‘this great and unrivalled discovery for preserving the lives of our fellow creatures, will be rewarded by some mark of national distinction’.89 Many individual miners also signed tributes or letters of thanks. In September 1816 ‘we, the undersigned miners at the Whitehaven Collieries’ thanked Davy for his ‘invaluable discovery of the safe lamps, which are to us life preservers’. They humbly wished it was in their power to offer more than this ‘tribute of gratitude’. The wording of the letter was obviously drawn up by an overseer, but the signatures were genuine, and must have moved Davy. The crumpled paper was laboriously signed by eighty-two miners, forty-seven of whom were illiterate, and put �
�x’ against their names.90
John Buddle, now entirely won over by Davy, was also concerned about a reward. By August there were 144 safety lamps ‘in daily use’ at Walls End, and they were rapidly spreading to all the other collieries in the North-East.91 Buddle urged Davy to take out a patent, pointing out that he could not only make his fortune but control the quality of the lamps issued to miners. Davy consistently refused, although he knew his colleague William Wollaston had made a fortune with a patent on processing platinum. Yet Davy was hugely proud of his achievement, and was never modest about it. On Banks’s recommendation he received the Rumford Medal from the Royal Society in 1817, and the following year was made a baronet by the Prince Regent. Davy designed his own coat of arms, showing the safety lamp encircled with a Latin motto which announced: ‘I Built the Light which brings Safety’.92
His reputation was now international. He received acknowledgements from miners in Alsace, Flanders, Austria and Poland. Some years later the Tsar of Russia, Alexander I, sent him a large silver goblet. At home the Edinburgh Review ran an enormous article in praise of his work, written by none other than the brilliant geologist who had once paid court to Jane Apreece, Professor John Playfair. ‘It may fairly be said that there is hardly in the whole compass of art or science a single invention of which one would rather wish to be the author.’ Playfair described the discovery as the result of pure inductive science, ‘in no degree the effect of accident’, and ‘as wonderful as it is important’. Its historic significance was unmistakeable. ‘This is exactly such a case as we should choose to place before Bacon, were he to revisit the earth, in order to give him, in a small compass, an idea of the advancement which philosophy has made, since the time when he pointed out to her the route which she ought to pursue.’ Here the word ‘philosophy’ was used exclusively to mean ‘science’ in the modern sense: what Playfair defined as ‘the immediate and constant appeal to experiment’.93
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