CANTON, John, an ingenious natural philosopher, born at Stroud in Gloucestershire, in 1718. Among those with whom he became acquainted in early life was Dr Henry Miles of Tooting, a member of the Royal Society, and of approved eminence in natural science and philosophy. This gentleman perceiving that Mr Canton possessed abilities too promising to be confined within the narrow limits of a country town, prevailed on his father to permit him to go to London. Accordingly he arrived at the metropolis in March 1737, and resided with Dr Miles at Tooting till the 6th of May following, when he articulated himself for the term of five years as a clerk to Mr Samuel Watkins, master of the academy in Spital Square. In this situation, his ingenuity, diligence, and conduct were so conspicuous, that on the expiration of his clerkship in May 1742 he was taken into partnership with Mr Watkins for three years. He afterwards succeeded that gentleman in Spital Square, and there continued during the remainder of his life. In 1744 he married Penelope, the eldest daughter of Mr Thomas Colbrooke.
Towards the end of 1745, electricity, which seems early to have engaged Canton's notice, received a very important improvement by the discovery of the Leyden phial. This event turned the thoughts of most of the philosophers of Europe to that branch of natural philosophy; and Canton, who was one of the first to repeat and to pursue the experiment, found his assiduity and attention rewarded by many
valuable discoveries. Towards the end of 1749 he was concerned with his friend Benjamin Robins in making experiments in order to determine to what height rockets may be made to ascend, and at what distance their light may be seen. In 1750 was read at the Royal Society Canton's "Method of making Artificial Magnets, without the use of, and yet far superior to, any natural ones." This paper procured him the honour of being elected a member of the society, and the award of their gold medal. The same year he was complimented with the degree of M. A. by the University of Aberdeen; and in 1751 was chosen one of the council of the Royal Society.
In 1752 Canton was so fortunate as to be the first person in England who, by attracting the electric fire from the clouds during a thunder-storm, verified Dr Franklin's hypothesis of the identity of lightning and electricity. Next year his paper entitled "Electrical Experiments, with an attempt to account for their several phenomena," was read at the Royal Society. In the same paper he mentioned his having discovered, by a great number of experiments, that some clouds were in a positive, and some in a negative, state of electricity. Dr Franklin, much about the same time, made a similar discovery in America. This circumstance, together with Canton's constant defence of the doctor's hypothesis, induced that philosopher immediately on his arrival in England to pay him a visit, and gave rise to a friendship which ever afterwards continued without interruption. In the Lady's Diary for 1756, Canton answered the prize question that had been proposed in the preceding year. The question was, "How can what we call the shooting of stars be best accounted for; what is the substance of this phenomenon; and in what state of the atmosphere doth it most frequently show itself?" and the solution, though anonymous, proved so satisfactory to his friend Mr Thomas Simpson, who then conducted that work, that he sent Canton the prize, accompanied with a note, in which he said he was sure that he was not mistaken in the author of it, as no one besides, that he knew of, could have answered the question. Canton's next communication to the public was a letter in the Gentleman's Magazine for September 1759, on the electrical properties of the tourmalin, in which the peculiarities of that stone are stated in a very concise and elegant manner. On the 13th December, in the same year, was read at the Royal Society a paper of his entitled "An attempt to account for the regular diurnal variation of the Horizontal Magnetic Needle; and also for its irregular variation at the time of an Aurora Borealis." A complete year's observations of the diurnal variations of the needle are annexed to this paper. On the 5th November 1761, he communicated to the Royal Society an account of the Transit of Venus, 6th June 1761, observed in Spital Square. His next communication to the Society was a letter addressed to Dr Franklin, and read in February 1762, containing some remarks on Mr Delaval's electrical experiments. On the 16th December in the same year he published a paper entitled "Experiments to prove that water is not incompressible." These experiments are a complete refutation of the famous Florentine experiments, which so many philosophers have mentioned as a proof of the incompressibility of water. On St Andrew's day 1763, he was for the third time elected one of the council of the Royal Society; and on the 8th November in the following year were read before that learned body his further "Experiments and observations on the compressibility of water and some other fluids." The establishment of this fact, in opposition to the received opinion, formed on the hasty decision of the Florentine Academy, was thought to be deserving of the society's gold medal. It was accordingly moved for in the council of 1764; and after several invidious delays, which terminated much to his honour, it was presented to him on the 30th November 1766.
His next communication to the Royal Society was made in December 1768, entitled "An easy method of making a phosphorus that will imbibe and emit light like the Bolognian stone; with experiments and observations." The dean and chapter of St Paul's having, in a letter to the president, dated 5th March 1769, requested the opinions of the Royal Society relative to the best and most effectual method of fixing electrical conductors to preserve that cathedral from damage by lightning, Canton was one of the committee appointed to take the letter into consideration, and to report upon it. The gentlemen joined with him in this business were Dr Watson, Dr Franklin, Mr Delaval, and Mr Wilson. Their report was made on the 8th of June following, and the method recommended by them was carried into execution. The last paper of Canton's which was read before the Royal Society was on the 21st December 1769, contained "Experiments to prove that the Luminousness of the Sea arises from the putrefaction of its animal substances." Besides these, he wrote a number of papers both in earlier and in later life, which appeared in several publications, and particularly in the Gentleman's Magazine.
The close and sedentary life of Canton, arising from an unremitting attention to the duties of his profession, and to the prosecution of his philosophical inquiries and experiments, probably contributed to shorten his days. He died of a dropsy in the chest, on the 22d of March 1772.