The honour of being the true inventor of ventilators of ships and mines was a question of dispute between the Swede Mårten Triewald and Stephen Hales. British scholars generally give the credit to Hales. His paper, A Description of Ventilators where by Great Quantities of Fresh Air may with Ease be Conveyed into Mines, Goals, Hospitals, Workhouses and Ships . . . was published in London, 1743. DSB states ”after a victory over a rival inventor, Hales’ ventilators was installed in His Majesty’s ships, in merchant vessels, in slave ships, and in hospitals and prisons.” The ’rival inventor’ was Triewald, who lived in England for ten years. He already in 1740 discusses the ventilation in mines in the Transactions of the Royal Swedish Academy of Science (KVAH, vol. I, 1740, pp 444-51). Garrison-Morton 1596 gives Stephen Hales as the inventor of artifical ventilation. His book was published in 1743. In the present treatise on the use of ventilators in ships, Triewald’s privilege of his invention, dated 10 October, 1741, is printed on verso of the title-leaf. There is no printing date but the paper was read before the Academy of Science on April 3rd, 1742, and published soon after in the same year upon recommendation of the Academy - even if Triewald later refers to it as being published in 1741. Later on, when Triewald had been acquainted with the contents of Hales’ book (1743), he returned to the matter by claiming Hales to have borrowed the whole idea from him and also that Hales’ ventilators had some serious faults compared with his own (KVAH, 1744, pp 251-60, with two folding plates, Tab. VII and VIII). That Triewald’s invention was the first in print is evident as Hales refers to Triewald’s invention of 1741 in the preface to his own book of 1743. Among the thumbnails we also show one of the two plates accompanying Triewald’s paper in KVAH 1744. Collation: Pp (12). Binding: As issued, with a marbled spine strip.