William Parsons, 3rd Earl of Rosse, Baron of Oxmantown, 6th Baronet of Birr Castle, was born in June of 1800 to Lord Laurence Parsons, 2nd Earl of Rosse, and Lady Alice Lloyd. He served as a Member of Parliament from 1821-1834. Lord Rosse married Lady Mary Field, daughter of John Wilmer Field on 14 April 1836. Upon the death of his father, Laurence Parsons, 2nd Earl of Rosse in 1841, William became the 3rd Earl of Rosse. He was also President of the British Association from 1843-1844. Lord Rosse was president of the Royal Society from 1845-1854, while he also served as an Irish representative peer. From 1862-1867 he was chancellor of Trinity College, Dublin. Lord Rosse was an avid scientist, a passion that he shared with his wife, Mary Rosse, and is best known for building the 'Leviathan of Parsonstown,’ a 72-inch telescope. It was built in 1845 and was the largest telescope in the world. As an astronomer, he was first to discover the spiral nature of some nebulae (now called spiral galaxies), and naming the Crab Nebula. He died 31 October 1867, and was succeeded by his son, Laurence Parsons, 4th Earl of Rosse.