(John), whose discoveries in chemistry have astonished the scientific part of the public, defend- ed, says Wood, from a gentled family living at Brete in the county of Cornwall. His father was probably a younger son, bred to business; for our author was born in Fleet-street, London, in the parish of St Dunstan's in the West. At what school he received the rudiments of his education, a circumstance which the biographers of men eminent in the republic of letters should never omit, we have not been able to learn; but on the 27th of September 1661, when he had just completed his 16th year, he was admitted a scholar of Wadham college, Ox- ford. Some time afterwards, on the recommendation of Henry Coventry, Esq.; one of the secretaries of state, he was chosen probationer fellow of All-souls college. As Wood informs us that he had here a Legist's place, an expression by which we understand a law-fellowship; it is not wonderful that he took his degrees in the civil law, though physic and the physical sciences were the favourite objects of his study. He was indeed an emi- nent physician, practising both in London and in Bath, but in the latter city chiefly in the summer months, till the year 1679, when he died, some time during the month of September, in the house of an apothecary in York-street, Covent Garden, and was buried in the church of that parish. He had been married, says Wood, a little before his death, not altogether to his content; and indeed he must have been very discontented, if he chose to die in the house of a friend rather than in his own. He published, "Tractatus quinque medicis phy- sici," 1. De salinitro; 2. De respiracione; 3. De respira- tione factus in utero et oro; 4. De motu musculari et spiritibus animalibus; 5. De Rachitide." These were published together in 8vo at Oxford, in 1674; but there is an edition of two of them, "De respiracione," and "De Rachitide," published together at Leyden in 1671.

The fame of this author has been lately revived and extended by Dr Beddoes, who published, in 1790, "Chemical Experiments and Opinions, extracted from a work published in the last century," 8vo; in which he gives to Mayow the highest credit as a chemist, and attributes to him some of the greatest modern discoveries respecting air, giving many extracts from the three first of his treatises. His chief discovery was, that oxygen gas, to which he gave the name of fire air, exists in the nitrous acid, and in the atmosphere; which he proved by such decisive experiments, as to render it impossible to explain how Boyle and Pates could avoid availing themselves, in their researches into air, of so capital a discovery. Mayow also relates his manner of passing uniform fluids under water, from vessel to vessel, which is generally believed to be a new art. He did not col- lect dephlogisticated air in vessels, and transfer it from one jar to another, but he proved its existence by find- ing substances that would burn in vacuo, and in water when mixed with nitre; and after animals had breath- ed and died in vessels filled with atmospheric air, or af- ter fire had been extinguished in them, there was a re- siduum which was the part of the air unfit for respira- tion, and for supporting fire; and he further shewed, that nitrous acid cannot be formed, but by exposing the substances that generate it to the atmosphere. Mayow was undoubtedly no common man, especially since, if the above dates are right, he was only 34 at the time of his death. But he was not so unknown as Dr Bed- does supposed; for since the repetition of the same dis- covery by Priestley and Scheele, reference has frequent- ly been made by chemists to Mayow as the original in- ventor; thus allowing to him a species of merit, to which he has perhaps but a doubtful claim, and which, if that claim be well founded, must certainly be shared between him and Dr Hooke. See Hooks in this Supplement.