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 artificial ventilators. The method of injecting air with bellows he applied to the ventilation of prisons, ships, granaries, &c. By means of a correspondence with Du Hamel, the well-known naturalist, he succeeded in getting his invention fitted to the French prisons in which English prisoners were confined. On this occasion ‘the venerable patriarch of Teddington was heard merrily to say “he hoped nobody would inform against him for corresponding with the enemy.”’ By a curious coincidence a method of ventilating similar to Hales's was brought out at the same time (1741) by Martin Triewald, captain of mechanics to the king of Sweden. The diminution in the annual mortality at the Savoy prison after Hales's ventilator had been put up seems to have been very great. Newgate also benefited in the same way.

In a letter to Mark Hildesley, bishop of Sodor and Man (, Life of Hildesley, 1799), Hales writes, in 1758, of having for the last thirty years borne public testimony against drams ‘in eleven different books or newspapers,’ and adds that this circumstance ‘has been of greater satisfaction to me than if I were assured that the means which I have proposed to avoid noxious air should occasion the prolonging the health and lives of an hundred millions of persons.’ It would seem from this that he believed his efforts against spirit-drinking to have had a beneficial effect. His writings on this subject were certainly popular. His anonymous pamphlet, ‘A Friendly Admonition to the Drinkers of Brandy,’ &c., 1734, went through several editions, a sixth being published by the Society for the Promotion of Christian Knowledge in 1807. In another pamphlet, ‘Distilled Spirituous Liquors the Bane of the Nation,’ 1736, he shows the general evil arising from spirit-drinking, and seeks to rouse the interest of the landed classes by showing that dram-drinkers lose their appetites and lower the demand for provisions. The injury to the landed interest thus caused by the distillers of London he estimates at 600,000l. annually.

Hales made experiments or suggestions on the distillation of fresh from salt water; on the preservation of water and of meat in sea-voyages; on the possibility of bottling chalybeate waters; on a method of cleansing harbours; on a ‘sea-gage’ to measure unfathomable depths, the idea of which he took from the mercurial gauge with which he measured the pressure exerted by peas swelling in water; on a plan for preserving persons in hot climates from the evil effects of heavy dews; on the use of furze in fencing river banks; on winnowing corn; on earthquakes; on a method of preventing the spread of fires; on a thermometer for high temperatures; on natural purging waters, &c.

His portrait by Francis Cotes, R.A., was engraved by Hopwood, and published in R. J. Thornton's ‘Elementary Botanical Plates,’ 1810; more recently as a woodcut in the ‘Gardener's Chronicle,’ 1877, p. 17. He was also painted by Hudson, and a 12mo portrait was engraved in mezzotint by McArdell, probably from this portrait. His monument in Westminster Abbey has a bas-relief in profile by Wilton.

Hales's principal works are: 1. ‘Vegetable Staticks; or an Account of some Statical Experiments on the Sap in Vegetables … also a Specimen of an Attempt to Analyse the Air …’ London, 8vo, 1727. 2. ‘Statical Essays,’ containing: vol. i. ‘Vegetable Staticks;’ vol. ii. ‘Hæmastaticks: or an Account of some Hydraulick and Hydrostatical Experiments made on the Blood and Blood-Vessels of Animals: with an Account of some Experiments on Stones in the Kidney and Bladder; … to which is added an Appendix containing Observations and Experiments relating to several Subjects in the first Volume,’ 8vo, London, 1733. 3. ‘A Friendly Admonition to the Drinkers of Brandy and other Distilled Spirit’ (anon.), London, 8vo, 1734. 4. ‘Distilled Spirituous Liquors the Bane of the Nation; being some considerations humbly offered to the Hon. the House of Commons, &c., &c. To which is added an Appendix containing the late presentments of the Grand Juries,’ &c., January 1735–6, London, 8vo, 1736. 5. ‘Philosophical Experiments: containing useful and necessary Instructions for such as undertake long Voyages at Sea; showing how Sea-water may be made fresh and wholesome, and how Fresh Water may be preserved sweet; how Biscuit, Corn, &c., may be secured from the Weevel, Maggots, and other Insects; and Flesh preserved in Hot Climates by salting Animals whole; to which is added an account of several Experiments and Observations on Chalybeate or Steel-waters, with some Attempts to convey them to distant places, preserving their virtue to a greater degree than has hitherto been done; likewise a proposal for Cleansing away Mud, &c., out of Rivers, Harbours, and Reservoirs,’ London, 8vo, 1739. 6. ‘An Account of some Experiments and Observations on Mrs. Stephens's Medicines for Dissolving the Stone …’ 8vo, London, 1740. 7. ‘A Description of Ventilators [and] a Treatise on Ventilators,’ 2 vols. 8vo, London, 1743 and 1758. 8. ‘An Account of some Experiments and Observations on Tar-Water …,’ London, 8vo, 1745. 9. ‘An