Page:Dictionary of National Biography, Third Supplement.djvu/467

 a drawing by Legros, the original of a well-known etching, and a bust by Dalou are in the possession of the family; an autograph portrait is in the Uffizi Gallery, and pictures by (Sir) Arthur Cope and Seymour Lucas, both painted in 1911, belong to the Royal Academy; an excellent likeness by Sir Philip Burne-Jones is in the National Portrait Gallery, and another is introduced into the vast group of the ‘Hanging Committee’ by Sir H. von Herkomer in the Tate Gallery; there is also a bas-relief showing his head (life-size) by W. R. Colton, R.A. (Royal Academy Pictures, 1911 and 1920).

Poynter was probably, with the exception of Alfred Stevens, the most versatile and accomplished academic draughtsman the English school has ever produced. He loved drawing for its own sake, and put the best of himself into the numberless studies from life which he made for even the most inconspicuous details of his paintings. As happened with the old masters in similar circumstances, the spirit frequently lost force in the process of transference to the finished picture, especially as Poynter was a deliberate worker and, as he himself was fully aware, although a sound never a brilliant manipulator of oil paint. His water-colours show perfect mastery of the medium according to the principles of the school to which he belonged. His work in fresco has been mentioned. He executed a few very original medals and designed reverses for the coinage of 1894. Representative series of his drawings are in the British and Victoria and Albert museums. In addition to the works in public galleries already noted, others are at Birmingham, Manchester, and Bristol.

 POYNTING, JOHN HENRY (1852–1914), physicist, the youngest son of the Rev. T. Elford Poynting, Unitarian minister at Monton, near Manchester, by his wife Elizabeth Long, of Bath, was born at Monton 9 September 1852. He received his earlier education at the school kept by his father, and then went in 1867 to the Owens College, Manchester (now the university of Manchester). He took the B.Sc. degree at London University in 1872. In the same year he gained an entrance scholarship at Trinity College, Cambridge, and came into residence at Cambridge in October. He took his degree in 1876, being placed third in the list of the mathematical tripos. Immediately afterwards he went back to the Owens College and demonstrated in the physical laboratory under Balfour Stewart [q.v.]. On his election to a fellowship at Trinity College in 1878 Poynting returned to Cambridge, and began in the Cavendish laboratory, under James Clerk Maxwell [q.v.], experiments on the mean density of the earth which occupied much of his time for the next ten years. He remained at Cambridge until 1880, when he was elected to the chair of physics in Mason College, Birmingham (now the university of Birmingham), which had just been founded. This post he held until his death. In 1887 he received the Sc.D. of Cambridge and in 1888 he was made a fellow of the Royal Society; in 1893 the Adams prize was awarded to him, and the Hopkins prize in 1903. He was president of Section A of the British Association in 1899, and president of the Physical Society in 1905. In the latter year he received a royal medal from the Royal Society ‘for his researches in physical science, especially in connexion with the constant of gravitation and the theories of electro-dynamics and radiation’. He was a vice-president of the Royal Society in 1910–1911.

Poynting's most important contributions to physics are two papers communicated to the Royal Society: On the Transfer of Energy in the Electromagnetic Field (Philosophical Transactions, A, 1884), and On the Connexion between Electric Currents and the Electric and Magnetic Induction in the Surrounding Field (ibid., 1885). These papers revolutionized ideas about the motion of energy in the electric field. To take an example: before the publication of these papers, when a charged Leyden jar was discharged by connecting the inside and outside by a wire, the energy was supposed to travel along the wire much in the same way as hydraulic power is carried through a pipe. In Poynting's view the energy spreads out from the glass between the coatings of the jar and then converges sideways into the wire, where it is converted into heat. He showed that there was a general law for the transfer of energy, according to which it moves at any point perpendicularly to the planes containing the direction of the electric and magnetic forces, and the amount crossing unit area per second is equal to the product of these forces multiplied by the sine of the angle between them and 441