STEPHEN, D. D. a celebrated divine and philosopher, was born in 1677. He was the sixth son of Thomas Hales, Esq. the eldest son of Sir Robert Hales, created a baronet by King Charles II. and Mary the heiress of Richard Langley of Abbots-Wood in Hertfordshire. In 1696 he was entered a pensioner at Bennet-college, Cambridge; and was admitted a fellow in 1703, and became bachelor of divinity in 1711. He soon discovered a genius for natural philosophy. Botany was his first study; and he used frequently to make excursions among Gogmagog hills, in company with Dr Stukeley, 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 have wings. In company 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; in which, however, they did not make any remarkable discoveries. In the study of astronomy Mr Hales was equally affiduous. Having made himself acquainted with the Newtonian system, he contrived a machine for showing the phenomena on much the same principles with that afterwards made by Mr 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 afterwards accepted of 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 after, he married Mary, the daughter and heiress of Dr Newce, who was rector of Halifham 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 6th of March, in the year following, he exhibited an account of some experiments he had lately made on the effect of the sun's warmth 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 with great pleasure; and on the 14th of June 1725 exhibited a treatise in which he gave an account of his progress. This treatise being highly applauded by the Society, he farther enlarged and improved it; and in April 1727 he published it under the title of Vegetable Statics. This work he dedicated to his late majesty King George II. who was then prince of Wales: and he was the same year chosen one of the council of the Royal Society, Sir Hans Sloane being at the same annual election chosen their president. The book being well received, a second edition of it was published in 1731. In a preface to this edition Mr Hales promised a sequel to the work, which he published in 1733 under the title of Statical Effects, &c. 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 for the degree of doctor in divinity; a mark of distinction the more honourable, as it is not usual for one university to confer academical honours on those who are educated at another. In 1734, when the health and morals of the lower and middling classes 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. The latter end 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. His text was, "Bear ye one another's burthens, and so fulfil the law of Christ;" Galatians vi. 2. In 1739 he printed a volume in 8vo, 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 farther experiments towards the discovery of medicines for dissolving the stone in the kidneys and bladder, and preserving meat in long voyages; for which he received the gold medal of Sir Godfrey Copley's donation. The year following he published some account of Experiments and Observations on Mrs Stephen's Medicines for dissolving the Stone, in which their dissolvent power is enquired into and demonstrated.

In 1741 he read before the Royal Society an account of an instrument which he invented, and called a ventilator, for conveying fresh air into mines, hospitals, prisons, and the close 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, called captain of mechanics, for which the king and senate granted him a privilege in October following, and ordered every ship of war in the service of that state to be furnished with one of them; a model also of this machine was sent into France, and all the ships in the French navy were also ordered to have a ventilator of the same sort. It happened also, 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 out of 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 among others Dr Mead and the ingenious Mr Benjamin Robins gave their testimony in its favour (see Air-Pipes). 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 to life, particularly for keeping corn sweet, by blowing through it fresh showers of air; a practice very soon adopted by France, a large granary having been made, under the direction of Duhamel, for the preservation of corn in this manner, with a view to make it a general practice.

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 by the publication of a work called Sirius, in which the learned and most excellent 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, by a letter to the editor of the Gentleman's Magazine, a description of a back-heaver, which will 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 dealers, who want to keep small quantities of corn for some time, but have no proper granary or repository for that purpose. He also 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 may 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 their Transactions. In the Gentleman's Magazine for July 1747, he published an account of a very considerable improvement of his back-heaver, by which it became capable of clearing corn of the very small grain, seeds, blacks, flint-stones, &c. to such perfection as to make it fit for feed-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 their Transactions. 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 the right hon. Henry Fox, Esq. then secretary at war, afterwards Lord Holland; and the benefit was so great, that though 50 or 100 in a year often died of the gaol distemper before, yet from the year 1749 to the year 1752 inclusive, no more than four persons died, though in the year 1750 the number of prisoners was 240; and of those four, one died of the small-pox, and another of intemperance. In the year 1750 he published some considerations on the causes of earthquakes; occasioned by the flight 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 Jeffry's well, which is printed in the Philosophical Transactions.

Dr Hales had now been several years honoured with the esteem and friendship of his royal highness Frederick prince of Wales; who frequently visited him at Teddington, from his neighbouring palace at Kew, and took a pleasure in surprising him in the midst of those curious researches into the various parts of nature which almost incessantly employed him. Upon the prince's death, which happened this year, and the settlement of the household of the prince's dowager, he was, without his solicitation, or even knowledge, appointed clerk of the closet or almoner to her royal highness. In 1751 he was chosen 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 24 wards; and it appeared that the disproportion of those that died in the gaol before and after this establishment was as 16 to 7. He published also a farther 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 gaol-fever by working in Newgate.

On 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 in the Gentleman's Magazine some farther considerations about means to draw the foul air out of 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 the Doctor invented to measure unfathomable depths, was communicated to the public in the same miscellany: this paper was drawn up about the year 1732 or 1733, by the Doctor, for Colin Campbell, Esq. This gentleman employed the ingenious Mr Hawkbee 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 to enrich their memoirs with many useful articles from this time till his death, 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 farther preferment; but of farther preferment he was not desirous; for being nominated by his late majesty to a canonry of Windsor, he engaged the princes 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 should reduce him to the dilemma either of 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 would interrupt his habits of life, can scarce be imputed to his temperance and humility without impeaching his benevolence; for if he had no wish 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 into his power, in the reward of industry, the alleviation of distress, and the support of helpless indigence. He was, however, remarkable for social virtue 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; the constant ferenity 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, pursuant to his own directions, under the tower of the parish church, which he built at his own expence not long before his death. Her royal highness the princess of Wales erected a monument to his memory in Westminster abbey."