Admiral Fitzroy's domestic barometer, unsigned, Britain, 1861-1870

Admiral Robert Fitzroy devised this form of barometer to help people working at sea or in coastal villages to anticipate bad weather. Atmospheric pressure - the weight of air - is indicated by the fluctuating levels of mercury in an upended sealed tube in a barometer. Fitzroy was the captain of the Beagle during Darwin's voyages and was very aware of the importance of forecasting the weather. He was later made the first head of what was to become the UK Meteorological Office and introduced the first published daily weather forecasts in The Times in 1860.