Stephen Hales (17 September 16774 January 1761) was an English clergyman who made major contributions to a range of scientific fields including botany, pneumatic chemistry and physiology. He was the first person to measure blood pressure. He also invented several devices, including a ventilator, a pneumatic trough and a surgical forceps for the removal of bladder stones. In addition to these achievements, he was a philanthropist and wrote a popular tract on alcoholic intemperance.

Life

Stephen Hales was born in Bekesbourne, Kent, England. He was the sixth son of Thomas Hales, heir to Baronetcy of Beakesbourne and Brymore, and his wife, Mary (née Wood), and was one of twelve or possibly thirteen children. Thomas Hales (died 1692) predeceased his father, Sir Robert Hales; therefore Sir Robert's grandson, Sir Thomas Hales, 2nd Baronet (Stephen Hales' brother) succeeded to the baronetcy in December 1693. Although he was an ordinand studying divinity, Hales would have received his degree in the Classics, mathematics, natural sciences and philosophy while in Cambridge. Hales was admitted as a Fellow of Corpus Christi in 1703, the same year as he obtained the degree of Master of Arts, and was ordained as Deacon at Bugden, Cambridgeshire. He continued his theological and other studies in Cambridge, where he became friends with William Stukeley who was studying medicine. He attended chemistry lectures by Giovanni Francisco Vigani while at Cambridge. His interest in biology, botany and physiology is presumed to date from that time. Hales remained in Teddington for the rest of his life, except for occasional visits to his other parishes. He was an assiduous minister – in addition to parish duties he enlarged and repaired the church and commissioned a new water supply for the village – and well regarded although there is some evidence that his experimental work on animal physiology was viewed with misgivings. Pope, however was also a close friend of Hales and considered him the model of the man who loves his God.

In 1718 Hales was elected a fellow of the Royal Society and in the same year became rector of Porlock, Somerset, a post he held alongside the curacy of Teddington.

In 1720 he married Mary Newce, but she died the following year, probably in childbirth; there were no children and he never remarried. In 1723 he was installed as rector of Farringdon, Hampshire (which he held alongside Teddington by employing a curate in Farringdon). Hales spent his summers there and became a friend of Gilbert White, the naturalist, whose family lived nearby.

Hales's fame as a scientist grew from 1718 onwards, and by the mid part of the 18th century he had achieved an international reputation. after his death.

Work

Hales is best known for his Statical Essays. The first volume, Vegetable Staticks (1727), contains an account of experiments in plant physiology and chemistry; it was translated into French by Georges-Louis Leclerc, Comte de Buffon in 1735 and into Italian by Maria Angela Ardinghelli in Naples in 1750-1752. The second volume, Haemastaticks (1733), describes experiments on animal physiology including the measurement of the "force of the blood", i.e. blood pressure. Translated and annotated by Ardinghelli in 1756. Hales commented that "plants very probably draw through their leaves some part of their nourishment from the air". In Vegetable Staticks Hales prefigured the cohesion theory of water movement in plants, although his ideas were not understood at the time, so he did not influence the debate on water transport in plants in the 19th century. He also speculated that plants might use light as a source of energy for growth (i.e. photosynthesis), based on Isaac Newton's suggestion that "gross bodies and light" might be interconvertible.

In Vegetable Staticks Hales also described experiments that showed that "... air freely enters plants, not only with the principal fund of nourishment by the roots, but also thro' the surface of their trunks and leaves". While Hales' work on the chemistry of air appears primitive by modern standards, its importance was acknowledged by Antoine Lavoisier, the discoverer of oxygen. Most famously, Hales made measurements of blood pressure in several animal species by inserting fine tubes into arteries and measuring the height to which the column of blood rose. Hales also described the effects of hemorrhage and hemorrhagic shock by progressive exsanguination of animals and accompanying measurement of blood pressure. In a horse he observed that as death approached "the Mare fell into cold and clammy sweats". In addition, Hales took wax casts of the ventricle of the heart and estimated how much blood was pumped by the heart; correctly described the roles of the mitral valve and aortic valve during systole and diastole; explained the pulsations of arteries in terms of their elasticity and attributed the resistance to blood flow to friction due to the passage of blood through small blood vessels.

Hales's work on the growth pattern of long bones, demonstrating epiphyseal growth; his demonstration of spinal reflexes in the frog and his suggestion that electricity played a role in allowing nerves to control muscle function are also noteworthy.

Inventions and other work

thumb|Image of a Ventilation Bellows devised by Stephen Hales

thumb|Description du ventilateur (French edition of Description of ventilators), 1744

Bad air was thought to be a cause of ill-health and death in the 18th century. Death and disease were common in overcrowded ships and prisons. Hales was one of several people in the early 18th century (other notable inventors being John Theophilus Desaguliers, Mårten Triewald and Samuel Sutton) who developed forms of ventilators to improve air quality. Hales' ventilators were also used in preserving foods and drying grain.

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.

Philanthropy

thumb|[[Audience Given by the Trustees of Georgia to a Delegation of Creek Indians. Hales is shown standing on the extreme left behind a chair.]]

After the death of his wife, Hales became increasingly involved in philanthropic causes. In 1722 he became a corresponding member of the Society for Promoting Christian Knowledge, founded by Thomas Bray. In 1723 Bray became ill and appointed trustees, including Hales, to administer a bequest from Abel Tassin, Sieur d’Allone for 'The Conversion of Negroes Slaves in the West Indies'. Subsequently, Hales was also appointed a trustee for Bray's legacy for establishing parochial libraries in the American colonies. These charities became incorporated into a scheme led by James Oglethorpe to establish a charitable colony for the poor, 'honest industrious debtors' and persecuted (Protestant) foreigners. Hales may well have felt a personal commitment to this scheme since his brothers had been imprisoned for debt following the failure of the South Sea Company and one, William, died of Gaol Fever in Newgate Prison.

The genus of trees Halesia was named after him by John Ellis in 1759. The American Society of Plant Biologists awards the Stephen Hales Prize annually to a scientist for work in plant biology.

Publications

See also

  • Pneumatic chemistry
  • Physiology
  • Botany
  • History of botany

References

Further reading

  • Hales, Stephen (1727). Vegetable Staticks. London: W. and J. Innys – from the Missouri Botanical Garden's library
  • Hales, Stephen (1738). "Philosophical experiments: containing useful, and necessary instructions for such as undertake long voyages at sea. Shewing how sea-water may be made fresh and wholsome: and how fresh water may be preserv'd sweet. How biscuit, corn, &c. may be secured from the weevel, meggots, and other insects. And flesh preserv'd in hot climates, by salting animals whole. To which is added, an account of several experiments and observations on chalybeate or steel-waters ... which were read before the Royal-society, at several of their meetings", London: W. Innys and R. Manby
  • Stephen Hales at the Galileo Project — details on Hales's life and work
  • For a calendar of manuscript correspondence and writing of Stephen Hales see: D.G.C. Allan and R.E. Schofield, Stephen Hales. Scientist and philanthropist (London: Scolar Press, 1980), p. 178, and for his published writing see ibid p. 191
  • For Hales's work as parish priest of Teddington see: David G.C. Allan, Science, Philanthropy and Religion in 18th century Teddington: Stephen Hales DD, FRS, (1677–1761) (Twickenham: Borough of Twickenham Local History Society, 2004). This work contains reconstructions of the enlargement of St Mary's Church, Hale's copyhold parsonage house and a map of his drainage scheme (Map by Ken Howe).
  • For a general assessment see: David G.C. Allan, Hales, Stephen (1677–1761) in Oxford Dictionary of National Biography.
  • For the 2009 celebration of his life and work see The William Shipley Group for RSA History Newsletter no. 22 (Nov 2009)
  • For Hales's association with the Society of Arts see David G.C. Allan, 'Founder of the Society of Arts' group article in Oxford Dictionary of National Biography (online supplement, 2008)
  • Hales, Stephen (1727). Vegetable staticks – digital facsimile from the Linda Hall Library