Canton, John (DNB00)

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CANTON, JOHN (1718–1772), electrician, was born at Stroud on 31 July 1718. In his youth he manifested considerable aptitude for scientific studies. He was apprenticed to a broad-cloth weaver, and afterwards, in 1737, sent to London. Canton articled himself for five years to a school-master in Spital Square, London, with whom he subsequently entered into partnership. He appears to have contributed some new experiments for Priestley's ‘Histories of Electrical and Optical Discoveries,’ and he soon became so celebrated that Dr. Thomson speaks of Canton as ‘one of the most successful experimenters in the golden age of electricity.’ He was elected a fellow of the Royal Society on 22 March 1749, and was chosen a member of the council in 1751.

Canton verified Dr. Franklin's hypotheses as to the identity of lightning and electricity, and was the first Englishman to successfully repeat his experiments. He discovered that vitreous substances do not always afford positive electricity by friction, and that either kind, negative or positive, might be developed at will in the same glass tube. He was the first electrician to demonstrate that air is capable of receiving electricity by communication. In a paper read at the Royal Society on 6 Dec. 1753 he announced that the common air of a room might be electrified to a considerable extent, so as not to part with its electricity for some time. With Canton originated also those remarkable experiments on induction which led Wilke and Œpinus to the method of charging a plate of air. His inquiries led Canton to various discoveries and inventions, such as his electroscope and electrometer, and his amalgam of tin and mercury for increasing the action of the rubber of the electrical machine.

On 17 Jan. 1750 Canton read a paper before the Royal Society with the title ‘Method of making Artificial Magnets without the use of Natural ones,’ which was published in the ‘Philosophical Transactions,’ vol. xlvi. At the anniversary in 1751 the Copley medal was awarded to Canton by the Royal Society. In 1747, some years before he published his ‘Method,’ Canton had turned his attention to the production of magnets by an artificial manipulation. His son (William) informs us that the paper would have been communicated earlier to the Royal Society but for fear of injuring Dr. Gowin Knight, who made money by touching needles for compasses. In 1750 the Rev. J. Michell pub- lished a ‘Treatise on Artificial Magnets,’ in which he described several new processes for preparing them. He charged Canton with plagiarism. Priestley, a friend of Canton's, writes to Mr. William Canton, 20 Aug. 1785, informing him that Mr. Michell gives Canton the merit of being the first to make powerful artificial magnets. In 1769 Canton communicated to the Royal Society some experiments which seemed to prove that the luminous appearance occasionally presented by the sea arose from the presence of decomposing animal matter. Canton was the discoverer of that phosphorescent substance usually known as Canton's phosphorus, prepared by mixing calcined oyster shells with a little sulphur, which after exposure to the sunshine is luminous in the dark. In 1762 he demonstrated before the council of the Royal Society, and at their cost, the compressibility of water, in opposition to the well-known experiment of the Florentine academicians. Some objections having been made to their awarding him, in 1765, the Copley medal, Lord Morton on that occasion highly praised Canton, and hoped that ‘he would continue his ingenious researches to the advancement of natural knowledge.’ Canton contributed several articles to the ‘Ladies' Diary’ in 1739–40, and to the ‘Gentleman's Magazine’ between 1739 and 1761. Canton died on 22 March 1772.

[Priestley's History of Electrical Discoveries; Weld's History of the Royal Society, i. 509, ii. 32, 510; Life (by Canton's son) in Kippis's Biog. Brit.; Noad's Manual of Electricity; Aug. de la Rive's Treatise on Electricity.]

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