17 September 1677 – 4 January 1761

Scientist, Inventor and Clergy-man

Stephen Hales was an English clergyman and notable scientist, who made major contributions in a range of scientific fields and was the first person to measure blood pressure. He eventually becoming chaplain to Augusta, Dowager Princess of Wales, who, upon his death, raised a monument to him in Westminster Abbey.

Born in Kent, Stephen Hales was the grandson of Sir Robert Hales, Baronet of Beakesbourne and Brymore. Hales attended St Benedict’s, Cambridge, now known as Corpus Christi College, as an ordinand studying divinity, where he also covered the Classics, mathematics, natural sciences, and philosophy. In 1703, Hales was admitted as a Fellow at Cambridge, and ordained as a Deacon. He became friends with William Stuckeley at Cambridge, with whom he began the work he later completed as Haemastaticks. Within a few years, Hales was ordained as a Priest, and moved to Teddington, in Middlesex, remaining there for the rest of his life.

Hales was best known for his Statical Essays. He wrote about his experiments in plant physiology in his first volume Vegetable Staticks, published in 1727. He later followed this with Haemastaticks, published in 1733, where he describes his experiments in animal physiology. However, not everyone approved of his methods, even receiving criticism from his close friend Alexander Pope. Hales also described a range of other work in Haemastaticks, leading to the development of special forceps to enable the removal of bladder stones.

In Hales’ lifetime, bad air was thought to be the cause of ill health and he was one of several people to work on ventilators to improve air quality. His work on the subject, a Description of Ventilators, was published in 1743, and a Treatise on Ventilators followed later in 1758. Hales’ ventilators were used in granaries to dry and preserve grain. They were also in use in ships, prisons, and naval hospitals, to improve air quality, and to help prevent the spread of diseases. One of Hales’ ventilators, powered by a windmill, was commissioned for Newgate prison, where Typhus, known as Gaol Fever, led to many deaths. Although it’s now known that Typhus isn’t spread by air, following installation of the ventilator, less deaths were recorded.

Following his Statical essays, Hales was a recognised name in his lifetime - Voltaire even used him as a casual example in his advice to a journalist on handling scientific topics. He was still well regarded for some decades following his death and the popular image of him as clergyman-inventor carried on into the early years of the 19th century. Although Stephen Hales’ name is not now well known, his work influenced the scientists succeeding him, work which leads to the present day. In Allan and Schofield’s book, Stephen Hales: Scientist and Philanthropist, they consider Hales’ record to be one that “…any professional scientist of the 19th or 20th centuries would be proud. For an 18th century amateur, incidentally trained in science and devoting major portions of his time to religion, public duties and public service, it was a phenomenal achievement.”