Passing through Italy, they drove into Lucca a day ahead of the English army that had landed at Livorno, and received a surprising and rapturous welcome. The entire town, waiting outside the gates, cheered and ululated as they trotted past. The crowd did not care that the carriage carried no guns to drive the French out; all that mattered was that the passengers were English, and grandees too apparently, smiling and waving as they passed along the line of people. To Abbott Faraday wrote:
… since we have left the French dominions we have been received with testimonies of pleasure & gratitude as strong as it was possible for the tongue to express. At Lucca we found the whole population without the gates waiting for the English … The town was decorated in the most brilliant manner by colours, drapery and embroidery flying from every window, & in the evening general illuminations took place done as expressive of their joy at the deliverance from the French government, & the English were hailed everywhere as their Saviours.35
They arrived in Florence flushed and delighted. It was a glorious morning, enhanced by the good fortune of finding the best hotel, ‘a Palace both outside and inside’, as Faraday described it,36 and that is probably just what it was. For the next two days he took himself off on his strolls about town. He discovered the River Arno, admired the bridges, particularly Ponte Santa Trinità, with its ‘air so light and free one can scarcely imagine it to be of stone’.37 He walked to the Duomo, the Baptistery, considered climbing Giotto’s campanile for ‘the finest possible view of Florence & the environs’, and then on to the Piazza Signoria. The bronzes in these public areas caught his eye particularly – the Baptistery doors, ‘bronze and most beautifully cast’; in the square ‘the bronze is a fine figure of Perseus with the head of Medusa’.
The great object of the visit to Florence was to go with Sir Humphry to see the scientific instruments formerly in use at Accademia del Cimento, once the working place of Galileo, and by now in the Museo di Storia Naturale. Faraday told Abbott all about it: ‘here is a fine Museum of Natural History containing an immense quantity of things curious & instructive and some wax works in anatomy & botany of the most delicate kind. The collection of apparatus is numerous and rendered invaluable by the instruments of Galileo & the Duke of Tuscany.’38
He goes on to describe the telescope with which Galileo discovered the moons of Jupiter in 1610, the ‘vast quantity’ of electrical machines and apparatus, the magnets – one of which could support a weight of 150 pounds39 – and particularly the great lens that Grand Duke Ferdinand III had commissioned. There were minerals, shells, insects, and stuffed birds and their eggs. The last room ‘contains some singular specimens of carving and modelling representing the horrors of death in the Plague and in a sepulchre. There were some Egyptian mummies in the room, one of them opened.’40
For two days Sir Humphry and Faraday worked on iodine in the museum’s laboratory, and also began to prepare for a dramatic experiment to show that diamond is pure carbon, a chemically identical substance. They set the Duke’s lenses, the larger one fourteen or fifteen inches in diameter, out in the garden. It was a sunny morning, and they tested their strength and efficacy by putting a piece of wood at the focus. Instantly the wood burst into flame. These were also the days of the Feast of the Annunciation, celebrated in Florence with great excitement. Faraday recorded the atmosphere in his Journal: ‘The country people flocked into the town in their best attire, the women ornamented with enormously large ear-rings and an abundance of gold and silver lace about the head.’41 People were shouting, cannon firing, and fairground booths had been set up in the streets between the cathedral and the Annunziata. Faraday went into the cathedral ‘at about 11 o’clock’ and heard the Te Deum to the sound of trumpets and cannonfire: ‘The sound of the trumpet in so large an inclosed space produced a striking effect on the mind – the music beautiful.’
On Sunday morning, the Feast of the Annunciation, Sir Humphry set a diamond on a perforated dish mounted on a platinum rod inside a thick glass globe. This was filled with a stream of hydrogen, ignited to heat the diamond. They had moved the equipment out of the garden, and now they were upstairs in the museum, by a south-facing window. On a wooden framework to one side was an air pump whose iron arm and oiled joints glistened in the sunshine as Faraday gently wound them up and down. Adjacent was a bubbling retort with potassium chlorate being heated to produce oxygen. Pipes joined the pump to the globe and the globe to the retort. As the hydrogen was drawn out of the globe by the pump, the oxygen, with a huff and a sneeze, was drawn in. Thus, the diamond was bathed in an atmosphere of oxygen, as pure as Davy and Faraday could make it.42
They all kept an anxious eye on the sun, for the sky must be clear and the sun as high and as hot as possible to give the required heat to the lens. With the noise of the Annunciation crowds sussurating across the garden, and the bangs of the cannon going off at the cathedral, Sir Humphry adjusted the lenses. The large one, nearest to the window, took the sunlight first and focused it onto the smaller one, set about three and a half feet away. This focused the light yet again, into an intense, dazzling, severe point which passed sharply through the wall of the glass globe and fell like a pinprick onto the diamond. This too sparkled, glorying in the experiment, but nothing else seemed to be happening. For about three-quarters of an hour they let the heat point play on the diamond, adjusting the apparatus from time to time to let the wall of the globe cool and to compensate for the relentless motion of the sun. Then, ‘on a sudden Sir H Davy observed the diamond to burn visibly, and when removed from the focus it was found to be in a state of active and rapid combustion. The diamond glowed brilliantly with a scarlet light inclining to purple, and when placed in the dark continued to burn for about four minutes.’43
They must have cheered and danced, having achieved what many thought impossible, the creation of about seven hundred degrees centigrade of heat at a tiny point of light, and the sudden, incandescent, unearthly consumption into a pile of black dust of the hardest substance known to man. Cheers echoed in the distance from the celebrations of the Feast of the Annunciation, where the crowds were celebrating another creation at a tiny point, one which would generate more light and heat than any diamond.
Over the next few days they repeated the experiment. It failed once because the sun was not strong enough, but as they progressed they found they could light up and damp down the burning diamond at will. They tried the procedure in different atmospheres – with carbonic acid and nitrous oxide – but the prize of the experiment was the proof that diamond is pure carbon, one and the same as graphite, pure and black. The experiments went on so long, day by day across a week, that Faraday was too late on one of the days to get into the Uffizi to see the paintings. But it was an intense, magnificent and spectacular week, comparable in excitement to anything in the long months of laboratory work in London and Paris that Sir Humphry had shared with Faraday. It was a definitive instance of the star scientist creating spectacular effects to pluck one more certain fact from the bosom of nature.
The party left Florence early on Sunday, 3 April, a week after the first success with the burning glass. ‘In no place since I left England have I been so comfortable and happy,’ Faraday wrote.44 They had been welcomed to Italy as conquerors, and left Florence with a conquest of their own. ‘Englishmen are here respected almost to adoration,’ Faraday wrote to his mother from Rome, ‘and I proudly own myself as belonging to that nation which holds so high a place in the scale of European Powers.’
CHAPTER 7 Mr Dance’s Kindness Claims my Gratitude
On the way to Rome Sir Humphry became more buoyant than he seems to have been on other parts of the journey, and he spoke with excitement about the geological features of the landscape. The double success of the iodine discovery and the burning of diamonds must have loosened his tongue, for the geological information that Faraday writes down in the Journal is fuller