STEPHEN, a celebrated divine and philosopher, was born in the year 1677. He was the sixth son of Thomas Hales, the eldest son of Sir Robert Hales, created a baronet by King Charles II., and Mary, the heiress of Richard Langley of Abbotswood in Hertfordshire. In 1696 he was entered as a pensioner at Bennet College, Cambridge, was admitted a fellow in 1703, and became bachelor of divinity in 1711. He soon discovered a genius for natural philosophy; but botany was his first study; and he used frequently to make excursions among Gogmagog Hills, in company with Dr Stukely, with a view of prosecuting that study. In these expeditions he likewise collected fossils and insects, having contrived a curious instrument for catching such of the latter as had wings. In conjunction with this friend he also applied himself to the study of anatomy, and invented a curious method of obtaining a representation of the lungs in lead. They next applied themselves to the study of chemistry; but in this science they did not make any remarkable discoveries. In the study of astronomy Mr Hales was equally assiduous. Having made himself acquainted with the Newtonian system, he contrived a machine for showing the phenomena, on much the same principles with that afterwards constructed by Rowley, and, from the name of his patron, called an Orrery.

About the year 1710 he was presented to the perpetual cure of Teddington, near Twickenham, in Middlesex; and he afterwards accepted the living of Porlock in Somersetshire, which vacated his fellowship in the college, and which he exchanged for the living of Faringdon in Hampshire. Soon afterwards he married Mary, the daughter and heiress of Dr Newce, who was rector of Halisham in Sussex, but resided at Much-Haddam in Hertfordshire. On the 13th of March 1718, he was elected a member of the Royal Society; and on the 5th of March in the year following; he exhibited an account of some experiments which he had recently made on the effect of solar heat in raising the sap in trees. This procured him the thanks of the society, who also requested him to prosecute the subject. With this request he complied; and on the 14th of June 1725 exhibited a treatise, in which he gave an account of his progress. This production being highly applauded by the society, he further enlarged and improved it; and in April 1727 he published it, under the title of Vegetable Statics. He dedicated the work to his majesty King George II., who was then Prince of Wales; and he was the same year appointed one of the council of the Royal Society, Sir Hans Sloane being at the same annual election chosen their president. His book being well received, there was published in 1731 a second edition, in which Mr. Hales promised a sequel to the work, which he accordingly published in 1733, under the title of Statistical Essays. In 1732 he was appointed one of the trustees for establishing a new colony in Georgia. On the 5th of July 1733 the university of Oxford honoured him with a diploma, conferring the degree of doctor in divinity; a mark of distinction the more honourable, as it was not usual for one university to confer academical honours upon those who had been educated at another. In 1734, when the health and morals of the lower and middling class of people were subverted by the excessive drinking of gin, he published, though without his name, A Friendly Admonition to the Drinkers of Brandy and other Spirituous Liquors, which was twice reprinted. Towards the close of the same year, he published a sermon which he preached at St. Bride's before the rest of the trustees for establishing a new colony in Georgia. In 1739 he printed a volume in octavo, entitled Philosophical Experiments on Sea-water, Corn, Flesh, and other Substances. This work, which contained many useful instructions for voyagers, was dedicated to the lords of the admiralty. The same year he exhibited to the Royal Society an account of some further experiments towards the discovery of medicines for dissolving the stone in the kidneys and bladder, and preserving meat in long voyages; and for this he received the gold medal of Sir Godfrey Copley's donation. The year following he published some account of experiments and observations on Stephen's Medicines for dissolving the Stone, in which their dissolvent power is inquired into and demonstrated.

In 1741 he read before the Royal Society an account of an instrument which he had invented, and called a ventilator, for conveying fresh air into mines, hospitals, prisons, and the confined parts of ships. He had communicated it to his particular friends some months before; and it is very remarkable, that a machine of the same kind, for the same purpose, was in the spring of the same year invented by one Martin Triewald, an officer in the service of the king of Sweden, for which the king and senate granted him a privilege in October following, and ordered every ship of war in the service of that country to be furnished with one of them. A model of this machine was also sent into France, and all the ships in the French navy were in consequence ordered to have a ventilator of the same sort. It happened likewise, that about the same time one Sutton, who kept a coffee-house in Aldersgate Street, invented a ventilator of another construction, to draw off the foul air from ships by means of the cook-room fire; but poor Sutton had not interest enough to make mankind accept the benefit he offered them, though its superiority to Dr. Hales's contrivance was evident, and though Dr. Mead and Mr. Benjamin Robins gave their testimony in its favour. The public, however, is not less indebted to the ingenuity and benevolence of Dr. Hales, whose ventilators came more easily into use for many purposes of the greatest importance, particularly for keeping corn sweet, by blowing through it currents of fresh air; a practice very soon adopted by France, where a large granary was constructed, under the direction of Duhamel, for the preservation of corn in this manner, with a view to render the practice general.

In 1743, Dr. Hales read before the Royal Society a description of a method of conveying liquors into the abdomen during the operation of tapping; and it was afterwards printed in their Transactions. In 1745, he published some experiments and observations on tar-water, which he had been induced to make in consequence of the publication of a work called Siris, in which Dr. Berkeley, bishop of Cloyne, had recommended tar water as an universal medicine. On this occasion several letters passed between them on the subject, particularly with respect to the use of tar-water in the disease of the horned cattle. In the same year he communicated to the public, in a letter addressed to the editor of the Gentleman's Magazine, a description of a back-heaver, calculated to winnow and clean corn much sooner and better than can be done by the common method. He also, at the same time, and by the same channel, communicated to the public a cheap and easy way to preserve corn sweet in sacks; an invention of great benefit to farmers, especially to poor lessees, who want to keep small quantities of corn for some time, but have no proper granary or repository for the purpose. He likewise the same year took the same method to publish directions how to keep corn sweet in heaps without turning it, and to sweeten it when musty. He published a long paper, containing an account of several methods to preserve corn by ventilators; with a particular description of several sorts of ventilators, illustrated by a cut, so that the whole mechanism of them might be easily known, and the machine constructed by a common carpenter. He published also in the same volume, but without his name, a detection of the fallacious boasts concerning the efficacy of the liquid shell in dissolving the stone in the bladder. In 1746 he communicated to the Royal Society a proposal for bringing small passable stones soon, and with ease, out of the bladder; and this was also printed in the Transactions of that body. In the Gentleman's Magazine for July 1747 he published an account of an improvement of his back-heaver, by which it was rendered capable of clearing corn of the small grain, seeds, blacks, smut-balls, and other impurities, to such perfection, as to make it fit for seed-corn. In 1748 he communicated to the Royal Society a proposal for checking, in some degree, the progress of fires, occasioned by the great fire which happened that year in Cornhill; and the substance of this proposal was printed in the Transactions of the society. In the same year he also communicated to the society two memoirs, which are printed in their Transactions; one on the great benefit of ventilators, and the other on some experiments in electricity. In 1749 his ventilators were fixed in the Savoy prison, by order of Henry Fox, then secretary at war, and afterwards Lord Holland; and the benefit proved so great, that though previously fifty or a hundred in a year often died of the jail distemper, yet from the year 1749 till the year 1752 inclusive, not more than four persons died, though in the year 1750 the number of prisoners was two hundred and forty; and of those four, one died of the smallpox, and another of intemperance. In the year 1750 he published some considerations on the causes of earthquakes, occasioned by the slight shocks felt that year in London. The substance of this work was also printed in the Philosophical Transactions. The same year he exhibited an examination of the strength of several purging waters, especially of the water of Jessop's Well, which is printed in the Philosophical Transactions.

Dr. Hales had been several years honoured with the esteem and friendship of Frederick prince of Wales, who frequently visited him at Teddington, from his neighbouring palace at Kew, and took pleasure in surprising him in the midst of those curious researches which almost incessantly employed him. Upon the prince's death, which happened this year, and the settlement of the household of the princess-dowager, he was, without his solicitation, or even knowledge, appointed clerk of the closet, or almoner, to her royal highness. In 1751 he was appointed by the College of Physicians to preach the annual sermon called Crowne's Lecture; Dr William Crowne having left a legacy for a sermon to be annually preached on "the wisdom and goodness of God displayed in the formation of man." Dr Hales's text was, With the ancient is wisdom, and in length of days understanding (Job, xii. 12). This sermon, as usual, was published at the request of the college. In the latter end of the year 1752, his ventilators, worked by a windmill, were fixed in Newgate, with branching trunks to twenty-four wards; and it appeared that the disproportion of those who died in the jail before and after this establishment was as sixteen to seven. He published also a further account of their success, and some observations on the great danger arising from foul air, exemplified by a narrative of several persons seized with the jail-fever by working in Newgate.

Upon the death of Sir Hans Sloane, which happened in the year 1753, Dr Hales was elected a member of the Academy of Sciences at Paris in his room. The same year he published some further considerations about the means of expelling foul air from the sick-rooms of occasional army hospitals, and private houses in town. He also published many other curious particulars relative to the use and success of ventilators. The same year a description of a sea-gage, which he had invented to measure unfathomable depths, was communicated to the public. This paper was drawn up about the year 1732 or 1733, for Mr Colin Campbell; and the latter employed Mr Hawksbee to make the machine it describes, which was tried in various depths, and answered with great exactness. It was however lost near Bermuda. In 1754 he communicated to the Royal Society some experiments for keeping water and fish sweet with lime-water, an account of which was published in the Philosophical Transactions. He also continued from this time till his death to enrich their memoirs with many useful articles, particularly a method of forwarding the distillation of fresh from salt water, by blowing showers of fresh air up through the latter during the operation. In 1757 he communicated to the editor of the Gentleman's Magazine an easy method of purifying the air, and regulating its heat, in melon-frames and green-houses; also further improvements in his method of distilling sea-water.

His reputation and the interest of his family and friends might easily have procured him further preferment; but of this he was not desirous; for being nominated by his majesty to a canonry of Windsor, he engaged the princess to request his majesty to recall his nomination. That a man so devoted to philosophical studies and employments, and so conscientious in the discharge of his duty, should not desire any preferment which might reduce him to the dilemma of either neglecting his duty, or foregoing his amusement, is not strange; but that he would refuse an honourable and profitable appointment, for which no duty was to be done that could interrupt his habits of life, can scarcely be imputed to his temperance and humility, without impeaching his benevolence. If he had no desire of anything more for himself, a liberal mind would surely have been highly gratified by the distribution of so considerable a sum as a canonry of Windsor would have put in his power, in the reward of industry, the alleviation of distress, and the support of helpless indigence. He was, however, remarkable for the social virtues and sweetness of temper; his life was not only blameless, but exemplary in a high degree; he was happy in himself, and beneficial to others, as appears by this account of his attainments and pursuits; whilst the constant serenity and cheerfulness of his mind, and the temperance and regularity of his life, concurred, with a good constitution, to preserve him in health and vigour to the uncommon age of fourscore and four years. He died at Teddington in 1761, and was buried under the tower of the parish church, which he had built at his own expense not long before his death. Her royal highness the Princess of Wales erected a monument to his memory in Westminster Abbey.