# Dictionary of National Biography, 1885-1900/Rue, Warren de la

​RUE, WARREN de la (1815–1889), inventor and man of science, elder son of Thomas de la Rue, by Jane Warren, was born at Guernsey on 15 Jan. 1815 [see De La Rue, Thomas]. Warren was educated at the Collège Sainte-Barbe in Paris, and while still a lad entered his father's printing firm. He showed from the first a keen interest in chemistry, physics, and mechanics, which he studied privately. He applied his knowledge in his business, was one of the first to use electrotyping on a manufacturing scale, and with Edwin Hill invented the first envelope-making machine exhibited at the exhibition of 1851. But, although he did not leave business until late in life, his chief interest was in pure science. In 1836 he published his first paper, on a Daniell battery with neutral solutions of zinc and copper sulphates. In 1845 he attended the first of a course of lectures on practical chemistry at the College of Chemistry under August Wilhelm Hofmann (1818–1892). He formed a close friendship with Hofmann, and with his help carried out an important investigation on cochineal. In 1849 he edited with Hofmann the first two volumes of an English edition of the ‘Jahresbericht … der Chemie’ of Justus von Liebig and Heinrich Kopp. He was elected F.R.S. in 1850.
About this time, under the influence of James Nasmyth (1808–1890) [q. v.], De la Rue abandoned chemistry temporarily for practical astronomy, and in 1850 he published his first astronomical paper, which contained a beautiful drawing of Saturn. He had a small observatory built at Canonbury, which he provided with a 13-inch Newtonian reflecting telescope constructed after his own designs, the speculum being figured and polished with his own hands by a new method which embodied an important advance on that of William Lassell (Monthly Notices of the Royal Astronomical Society, 1852, vol. xiii.). In 1852 he turned his attention to celestial photography, in which he became pre-eminent. A daguerreotype of the moon had been shown by William Cranch Bond (1789–1859) of Cambridge (U.S.A.) at the exhibition of 1851; but De la Rue, stimulated by this achievement, devised the first uniformly successful method of lunar photography. He also, by taking photographs from slightly different aspects and recombining them stereoscopically, brought to light various new features on the moon's surface. In 1857 he showed that points on the lunar surface, possessing equal optical intensity for the eye, affect photographic plates differently. In the same year he removed his observatory to Cranford in Middlesex.
In 1854 Sir John Frederick William Herschel [q. v.] had suggested that daily photographs of the sun should be taken at the Kew Observatory, and De la Rue devised a photo-heliographic telescope for the purpose, known later as the ‘Kew heliograph.’ The instrument, which was first used in 1858, is described in the ‘Philosophical Transactions’ for 1862 (i. 362). In 1859 he presented to the British Association an extensive report on celestial photography in England. He directed the expedition which went from England to observe the solar eclipse of 18 July 1860 at Rivabellosa in Spain. De la Rue's observations ​on this eclipse, and those carried out by similar methods by Father Angelo Secchi (1818–1878) at Desierta de las Palmas, proved conclusively that the ‘red flames’ or ‘prominences,’ observed during eclipses, belong to the sun and not to the moon. ‘To De la Rue,’ says Lockyer (Contributions to Solar Physics, pp. 111, 112), ‘belongs the full credit of having solved this important question.’ In 1862 De la Rue communicated the results of the eclipse expedition to the Royal Society as the Bakerian lecture for the year. He now, in conjunction with Balfour Stewart [q. v.], the superintendent of, and Mr. Benjamin Loewy, observer to, the Kew Observatory, made a large number of observations of the sun and of sun-spots, the results being first published in three memoirs entitled ‘Researches in Solar Physics,’ printed privately in 1865–8, and later in the ‘Philosophical Transactions.’ In 1861 De la Rue obtained a stereoscopic view of a sun-spot, and this and further observations by himself and his colleagues strongly supported the suggestion of Alexander Wilson (1714–1786) [q. v.] of Glasgow, based on observations made in 1769–74, that sun-spots are depressions in the sun's atmosphere; the facular appendages were shown to occupy a higher position, and in most cases to lag behind the spots in their movement of rotation, the smaller velocity of rotation being accounted for on the supposition that they had been flung up from a considerable depth. From the study of over 660 sun-spots the three astronomers attempted, but with no decided success, to connect the frequency of sun-spots with planetary movements (Young, The Sun, p. 149). They confirmed R. Wolf's expression for the total area of sun-spots in terms of the number of groups of spots and of isolated spots, and the total number of spots visible. The Kew heliograph, after being used on the 1860 eclipse expedition and from May 1863 to 1872 at Kew, was transferred to the Greenwich Observatory, but is now again at Kew.
In 1873 De la Rue took an active part in the preparation for observing the transit of Venus in 1874, but, finding that night work had become too arduous for him, gave his telescope to the university of Oxford, removed from Cranford to Portland Place, and fitted up a private physical laboratory for himself and his friend Dr. Hugo Müller, with whom, although mainly occupied with astronomical work, he had carried out a number of chemical researches. The most important of these were on Rangoon tar (1859), glyceric acid (1859), and terephthalic acid (1861). The research on Rangoon tar led to a patent which proved very profitable financially. He continued in this laboratory with Dr. Müller an elaborate series of researches on the electric discharge through gases, which were begun in 1868 and continued to 1883. It cannot be said that the results led to any simple explanation of the complex phenomena observed, but they furnished a valuable series of data and have special interest in connection with the discharge of the aurora borealis. The experiments were carried out by means of a battery of constant cells, devised and gradually improved by the two experimenters, of which silver and zinc formed the electrodes, and fused silver chloride and a solution of zinc, sodium, or ammonium chloride formed the electrolytes. A similar cell had been described in 1853 in ‘Electric Telegraph in India’ (p. 14), by Dr. (afterwards Sir) William Brooke O'Shaughnessy [q. v.], whose priority De la Rue acknowledged (Phil. Trans. clxix. 55). The battery was gradually increased until in 1883 it contained fifteen thousand cells.
De la Rue, who had retired from business in 1869, returned to it on the death of a younger brother in 1870, but finally retired in 1880. He died on 19 April 1889. He had married, in 1840, Miss Georgiana Bowles, and left four sons and a daughter.
De la Rue received the gold medal of the Astronomical Society in 1862, a royal medal from the Royal Society in 1864, and the ‘prix Lalande’ for 1865 (Comptes Rendus de l'Académie des Sciences, lxii. 476) for his discoveries. He also received the honorary degrees of M.A. and D.C.L. at Oxford, was elected corresponding member of the French Academy of Sciences, was made commander of the legion of honour, and received many other honours from abroad. His application of photography to celestial objects, in which he displayed ‘unfailing fertility of invention,’ has been of the utmost service to physical astronomy. He gave money as well as his own time freely for the advancement of pure science, and showed exceptional kindness to younger scientific men. He was an original member of the Chemical Society, over which he presided from 1867 to 1869, and again from 1879 to 1880; he served first as secretary, and then from 1864 to 1866 as president of the Royal Astronomical Society, was for many years president of the London Institution, and from 1878 to 1882 secretary to the Royal Institution. He was also an early and active member of the Royal Microscopical Society.
The ‘Royal Society's Catalogue’ (continued to 1884) contains a list of fifty-five papers published independently by De la Rue (of which the majority appeared in the ‘Monthly ​Notices of the Royal Astronomical Society’ or the publications of the Royal Society); eighteen papers published in conjunction with Dr. H. Müller, one in conjunction with Dr. H. Müller and William Spottiswoode [q. v.], and ten in conjunction with Drs. Balfour Stewart and B. Loewy. He also had privately printed two tables (computed by A. Marth) for the reduction of solar observations (1875 and 1878), and other tables (1877).
[Besides the sources mentioned, Men of the Reign; Boase's Modern Engl. Biogr.; De la Rue's own papers, and obituary notices in the Times, 22 April 1889, Transactions of the Chemical Society (1890, p. 441), Nature, xl. 27, Monthly Notices of the Royal Astronomical Society, l. 155, by E. B. K[nobel], and also presidential address by Dr. John Lee (ib. 1862, xxii. 131); Sir F. A. Abel in the Transactions of the Chemical Society, 1896, pp. 586 et seq.; Jubilee of the Chemical Society, 1896; Roscoe and Schorlemmer's Chemistry, vol. iii. pt. iv. p. 451; Biograph and Review, 1881, vi. 75; Royal Microscopical Society's Journal, 1889, p. 474; Berichte d. deutschen chemischen Gesellschaft, 1889, p. 1169, by A. W. Hofmann; Quekett's Microscope, 3rd edit. pp. 475 et seq.; Miss A. M. Clerke's Hist. of Astronomy in the Nineteenth Century, 3rd edit. p. 190 passim; Wolf's Gesch. d. Astronomie (1877), passim, and Handbuch d. Astronomie, 1890–3, p. 537 and passim; Young's The Sun, passim; Lockyer's Chemistry of the Sun, pp. 101, 406; Proceedings of the Royal Society, 1864 xiii. 510, 1885 xxxix. 37 et seq. (R. H. Scott's History of the Kew Observatory); information kindly given by Mr. Ernest de la Rue, son of Warren de la Rue, Dr. Charles Chree, superintendent of the Kew Observatory, and Professor Arthur Schuster.]
P. J. H.