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Stephen Hales (1677-1761) was an English clergyman who made major contributions to a range of scientific fields including botany, pneumatic chemistry and physiology. He was also a philanthropist and wrote a popular tract on alcoholic intemperance. Hales is best known for his Statical Essays. The first volume, Vegetable Staticks (1727), contains an account of experiments in plant physiology and chemistry and a study thorough of transpiration; the loss of water from the leaves of plants. Hales' invention of the pneumatic trough to collect gases over water was a major technical advance. The second volume, Haemastaticks (1733), describes experiments on animal physiology including the measurement of the "force of the blood", i.e. blood pressure. Hales developed a ventilator to improve air quality. Hales' ventilators were large bellows, that were widely installed in ships, prisons and mines and were successful in reducing disease. Hales also experimented with ways of distilling fresh water from sea water; preserving water and meat on sea-voyages; measuring depths at sea; measuring high temperatures; and wrote on a range of subjects including earthquakes; methods of preventing the spread of fires; and comparative mortality rates in relationship to rural and urban parishes. He also designed and invented surgical forceps for the removal of bladder stones. He lived to be 84 and died after a short illness.
