Henry Cavendish (1731 – 1810)
Born into the aristocracy, with both the Duke of Devonshire and the Duke of Kent as grandfathers, his mother died when he was just two, after giving birth to his brother, Frederick. After Cambridge and the obligatory Grand Tour of Europe, he joined his father at Great Marlborough Street in Soho, his home until his father died. Initially he helped him conduct experiments on heat, electricity and magnetism, but later he used the house to conduct most of his electrical research and his chemical experiments.
Elected to Royal Society in 1760, his first publication in its Philosophical Transactions – ‘Factitious Airs’ – was not to come for another 6 years. However, unpublished records show he was way ahead of his time. He conducted ‘Experiments on Arsenic’ in 1764, and more experiments on the evolution of heat accompanying solidification and condensation the following year. Other discoveries included the determination of the specific gravity of carbon dioxide, and the demonstration that it could stop a flame burning in common air. Cavendish discovered nitric acid (HNO3), and proved that water was not an element but made up of gases. He searched for phlogiston – the combustible element in all materials – and determined it to be hydrogen; it would not be until the end of the century that Lavoisier’s theories regarding oxygen would gain common acceptance.
Upon the death of his father in 1783 he inherited a considerable fortune, and moved to a villa on Clapham Common where he set up a well-stocked laboratory and library. At the front of the house was a wooden stage, from which he could climb a large tree to make astronomical observations; a large thermometer on the roof became a landmark for miles around.
Nevertheless, he was indifferent to his wealth and continued to live as parsimoniously as before: his father had brought him up strictly, and Henry had lived for a long time on an annual allowance of £120. Little changed with the inheritance. He spent nothing on himself or on luxuries, and cared little about his appearance, always wearing a dated, crumpled, violet suit, frilled cuffs and a three cornered hat. His haphazard ways with money extended to others. When once attending a Christening, he discovered that it was customary to make a gift to the nurse, so reportedly stuck his hand in his pocket, pulled out a handful of gold guineas, and gave them to her without a second thought. Yet he could also be extremely careful: when making a contribution to a charity, he would discover the highest reported donation, and always match it exactly.
During his father’s life, Henry had always been allocated exactly five shillings – on top of his allowance – for each of his Royal Society Club dinners. These were his only public appearances, for he remained remarkably shy and reticent throughout his adult life. Even at these dinners he rarely spoke and never sat for a portrait: the only likeness of him ever produced was sketched during a dinner but without his knowledge.
He died as he had lived, alone at home on Clapham Common. Known to believe that prolongation of life would only prolong its miseries, Cavendish apparently called his valet to his room on February 24th 1810 and said, ‘Mind what I say, I am going to die. When I am dead, but not until then, go to Lord George Cavendish and tell him of the event. Go!’. Half an hour later the valet was called again and asked to repeat the instructions. When it was done Cavendish replied, ‘Right. Give me the lavender water and go.’ He died there and then.