PARSONS, Sir LAURENCE, fourth Earl of Rosse (1840–1908), astronomer, born at Birr Castle, Parsonstown, King's Co., Ireland, on 17 Nov. 1840, was eldest of four surviving sons of William Parsons, third earl of Rosse [q. v.], the astronomer. The youngest brother, Sir Charles Algernon Parsons, C.B., F.R.S. (b. 1854), is well known for his invention of the compound steam turbine, since applied to marine propulsion.
Known in youth by the courtesy title of Baron Oxmantown, co. Wexford, Laurence was educated at home, first under the tutorship of the Rev. T. T. Gray, M.A., of Trinity College, Dublin, and then of John Purser, LL.D., afterwards professor of mathematics in Queen's College, Belfast.
Subsequently he entered Trinity College, Dublin, graduating in 1864, but he was non-resident. He was early imbued with his father's spirit of inquiry. At his father's observatory at Birr he assisted in the workshops and met leading men of science. Succeeding in 1867 to the peerage on his father's death, Lord Rosse thenceforward divided his interests between the management of his estates and the pursuit of astro-physics. He was made sheriff of King's Co., Ireland, in 1867, and became a representative peer of Ireland in 1868. On 29 Aug. 1890 he was created a knight of the Order of St. Patrick. He was subsequently lord-lieutenant (1892–1908).
According to Dr. Otto Boeddicker (technical coadjutor at Birr Observatory), Rosse had 'an inherited genius for mechanical relations and contrivances, and endless were his ideas and designs, all of a most ingenious character.' His first scientific paper, 'Description of an Equatoreal Clock,' appeared in the 'Monthly Notices' of the Royal Astronomical Society (1866). This was followed by a classical memoir in practical astronomy, 'An Account of Observations of the Great Nebula in Orion, made at Birr Castle, with the three-feet and six-feet Telescopes, between 1848 and 1867,' published in the 'Philosophical Transactions' of the Royal Society. An elaborate drawing of the nebula (engraved by J. Basire) accompanied the paper, and was characterised by Dr. J. E. L. Dreyer (Monthly Notices Roy. Astron. Soc. Feb. 1909) as being 'always of value as a faithful representation of the appearance of the Orion nebula in the largest telescope of the nineteenth century.' This study completed, Rosse took up (1868-9) an investigation on the radiation of heat from the moon (see Proc. Roy. Soc. vols, xvii., xix.), which formed the subject of the Royal Society's Bakerian lecture for 1873 (Phil. Trans. vol. clxiii.), and occupied his attention for the greater part of his life, despite somewhat scant notice from the scientific world. At the Royal Institution (1895) he gave a lecture, 'The Radiant Heat from the Moon during the Progress of an Eclipse' (Proc. Roy. Inst. vol. xiv.). Two days after Rosse's death, Sir Howard Grubb, F.R.S., exhibited at the Dublin meeting of the British Association Rosse's new development of apparatus for lunar heat observation. Other contributions comprised 'The Electric Resistance of Selenium' (Phil. Mag. 1874); 'On some Recent Improvements made in the Mountings of the Telescopes at Birr Castle' (Phil. Trans. 1881); 'On a Leaf-arrester, or Apparatus for removing Leaves, &c., from a Water Supply' (Rept. Brit. Assoc. 1901).
Lord Rosse was elected chancellor of Dublin University in 1885, succeeding Earl Cairns, and held office till his death. In 1903, in association with the provost and members of the university, he issued an appeal for funds (subscribing liberally himself) to secure the erection and equipment of science laboratories in Trinity College; the project had a successful issue.
The University of Oxford conferred the honorary degree of D.C.L. in 1870, and Dublin and Cambridge Universities that of LL.D. in 1879 and 1900 respectively. Elected a fellow of the Royal Society on 19 Dec. 1867, he served on the council (1871-2, 1887-8), and was vice-president for those years. On 13 Dec. 1867 he was elected a fellow of the Royal Astronomical Society, and served on the council (1876–8). Rosse was president of the Royal Dublin Society (1887–92) and of the Royal Irish Academy (1896-1901). He was made an honorary member of the Institution of Mechanical Engineers in 1888.
He died at Birr Castle on 30 Aug. 1908, and was buried in the old churchyard of Birr. He married on 1 Sept. 1870 Frances Cassandra Harvey, only child of Edward William Hawke, fourth baron Hawke of Towton, by his second wife, Frances, daughter of Walker Fetherstonhaugh. He had issue two sons and one daughter. The elder son, William Edward Parsons, succeeded to the title.
Lord Rosse was interested in the prosecution of magnetic observations at Valencia Observatory, Ireland, and collected a sum of money in furtherance of that object. After his death the capital was transferred to the trusteeship of the Royal Society, and is known as the 'Rosse Fund.' By
