# Dictionary of National Biography, 1885-1900/Parsons, William (1800-1867)

​PARSONS, WILLIAM, third Earl of Rosse (1800–1867), astronomer, born at York on 17 June 1800, was eldest son of Sir Lawrence Parsons, second earl of Rosse [q. v.] whom he succeeded in the title and estates on 24 Feb. 1841, having previously, from 1807, borne the title of Lord Oxmantown. His education was conducted at home until 1818, when he entered Trinity College, Dublin. Thence, by his father's desire, he passed to Oxford, matriculated from Magdalen College on 1 Feb. 1821, and graduated first class in mathematics on 7 Dec. 1822. From 1823 till 1834 he was four times elected to represent the King's County in parliament, but resigned his seat in 1834 in order to secure leisure for philosophical pursuits. His experiments towards improving the reflecting telescope were begun in 1827 at his father's seat, Birr Castle, Parsonstown, King's County, their earlier results being communicated in 1828 and 1830 to Brewster's ‘Edinburgh Journal of Science’ (ix. 25, ii. 136, new ser.). There was as yet no established mode of procedure in the matter; the processes of the Herschels had not been made public, and everything had to be freshly contrived. Lord Oxmantown took his workmen from the immediate locality; the requisite tools and machinery, furnaces and ovens, were constructed on the spot. He invented in 1828 an engine for grinding and polishing specula by steam power, and, after laborious trials, decided upon an alloy of four atoms (126.4 parts) of copper with one atom (58.9 parts) of tin as their material; but the difficulties connected with large castings of an eminently brittle and refractory substance were overcome only by the exercise of inexhaustible patience and ingenuity.
At last, in 1839, a 3-ft. speculum was successfully cast and mounted as a Newtonian. The details of its construction were communicated to the Royal Society on 9 May 1840 (Phil. Trans. cxxx. 503), and the results of observations made with it upon some of the nebulæ, on 19 June 1844 (ib. cxxxiv. 321). The methods of work being now well under control, two specula, each six feet in diameter, four tons in weight, and of fifty-four feet focus, were cast, after various failures, in 1842 and 1843. The tube in which one of these was mounted was fifty-eight feet long, and seven in diameter. Dean Peacock walked through it with uplifted umbrella, and it was compared by Dr. Robinson, when erect, to one of the round towers of Ireland. It was slung in chains between two piers of masonry twenty-three feet apart, seventy long, and fifty high. Its horizontal movement was limited to about ten degrees on either side of the meridian; but it had a vertical range of nearly one hundred and ten degrees. The speculum was supported in this vast tube by a complex system of cast-iron platforms, triangles, and levers, skilfully adapted for the equable distribution of pressure. The cost of the entire machine was estimated at 20,000l. Observations with it were begun in February 1845, and Rosse showed his tact by employing its unprecedented light-gathering powers chiefly in the examination of nebulæ. Among the more immediate results of its application were the ​decomposition into stars of many such objects until then ranked as irresolvable, the discovery of the important class of spiral nebulæ, and the detection of a complex annular structure in many of the ‘planetary’ kind. A description of these results was laid before the Royal Society on 19 June 1850 (ib. cxl. 499), and was succeeded on 5 June 1861 by a paper ‘On the Construction of Specula of Six-feet Aperture, and a Selection from the Observations of Nebulæ made with them’ (ib. cli. 681). This embodied the results obtained during seven years from the examination of nearly all Sir John Herschel's nebulæ. Drawings, sketches, and descriptive extracts from the observatory journals were appended, and the series was continued by the present Earl of Rosse in the ‘Transactions’ of the Royal Dublin Society for 1880.
Rosse joined the Royal Astronomical Society in 1824, the Royal Society in 1831, acted as president of the latter body from 1849 to 1854, and received a royal medal in 1851 (Proceedings of the Royal Society, vi. 113). The university of Cambridge conferred upon him in 1842 an honorary degree of LL.D., and the Imperial Academy of St. Petersburg admitted him to membership in 1853. He was a knight of St. Patrick (1845), and Napoleon III created him a knight of the Legion of Honour at the close of the Paris Exhibition of 1855. He presided over the meeting at Cork in 1843 of the British Association, was a visitor of Maynooth College and the Royal Observatory, Greenwich, belonged to the senate of the Queen's University, sat on the royal commission of weights and measures, and became chancellor of the university of Dublin in 1862. His duties as a local magnate were meanwhile discharged with exemplary assiduity. He exercised an unstinted hospitality, was lord lieutenant of King's County from 1831, and colonel of its militia from 1834. In the House of Lords, to which he was elected in 1845 as one of the representative peers for Ireland, he devoted himself to committee business, but spoke against the repeal of the corn laws. During the famine of 1846–7 he spent nearly the whole of his Irish revenues on the relief of distress, co-operating, however, vigorously with the government, at the constant risk of his life, in the suppression of murderous societies. His knowledge of the country was evinced by his ‘Letters on the State of Ireland,’ London, 1847 (2nd ed. in same year), and in his ‘Few Words on the Relation of Landlord and Tenant in Ireland,’ London, 1867. The latter was commented upon in Isaac Butt's ‘The Irish People and the Irish Land,’ 1867.
Rosse died at Monkstown, co. Dublin, on 31 Oct. 1867, in consequence of the removal of a tumour on the knee. His long and painful illness was borne with admirable fortitude. He was buried in the old church of St. Brendan, Parsonstown. A mural tablet was put up in his honour in the new parish church, and a bronze statue, by J. H. Foley, was erected by public subscription in John's Place, Parsonstown, and unveiled by his widow on 21 March 1876. A sermon ‘On the Immortality of the Intellect’ (afterwards published) was preached by the Rev. John Hewitt Jellett [q. v.] on the occasion of his death. Estimable in all the relations of life, he pursued without pretension or self-seeking the combined careers of a philosopher, a patriot, and a philanthropist.
Rosse married, on 14 May 1836, Mary, elder daughter and coheiress of Mr. John Wilmer Field of Heaton Hall, Yorkshire. He had by her four sons, of whom the eldest is the present Earl of Rosse. Lady Rosse died on 22 July 1885.
Rosse not only realised a great enlargement of telescopic capacity, but placed the art of constructing reflectors on a new footing by publishing the details of his methods. He foresaw the necessity for working the telescopes of the future under specially favourable climatic conditions, and was the first to attempt the substitution of silvered surfaces for metallic specula (Report Brit. Assoc. 1851, ii. 12). His experiments in lunar photography led to no definitive result. He was a good chemist, and studied military and naval engineering. During the Crimean war he sent to the admiralty, where it probably still remains, an elaborate memoir on a plan (the first of its kind) devised by him for armour-plating ships. A portrait of him, by Catterson Smith, is in the possession of the Royal Society.
A. M. C.