Hitherto we have said nothing about the great reflecting telescope, of 40 ft. focal length and 4 ft. aperture, the construction of which is often, though mistakenly, regarded as his chief performance. The full description of this celebrated instrument will be found in the 85th volume of the _Transactions_ of the Royal Society. On the day that it was finished (August 28, 1789) Herschel saw at the first view, in a grandeur not witnessed before, the Saturnian system with six satellites, five of which had been discovered long before by C. Huygens and G. D. Cassini, while the sixth, subsequently named Enceladus, he had, two years before, sighted by glimpses in his exquisite little telescope of 6(1/2) in. aperture, but now saw in unmistakable brightness with the towering giant he had just completed. On the 17th of September he discovered a seventh, which proved to be the nearest to the globe of Saturn. It has since received the name of Mimas. It is somewhat remarkable that, notwithstanding his long and repeated scrutinies of this planet, the eighth satellite, Hyperion, and the crape ring should have escaped him. Herschel married, on the 8th of May 1788, the widow of Mr John Pitt, a wealthy London merchant, by whom he had an only son, John Frederick William. The prince regent conferred a Hanoverian knighthood upon him in 1816. But a far more valued and less tardy distinction was the Copley medal assigned to him by his associates in the Royal Society in 1781. He died at Slough on the 25th of August 1822, in the eighty-fourth year of his age, and was buried under the tower of St Laurence's Church, Upton, within a few hundred yards of the old site of the 40-ft. telescope. A mural tablet on the wall of the church bears a Latin inscription from the pen of the late Dr Goodall, provost of Eton College. See Mrs John Herschel, _Memoir of Caroline Herschel_ (1876); E. S. Holden, _Herschel, his Life and Works_ (1881); A. M. Clerke, _The Herschels and Modern Astronomy_ (1895); E. S. Holden and C. S. Hastings, _Synopsis of the Scientific Writings of Sir William Herschel_ (Washington, 1881); Baron Laurier, _Eloge historique_, Paris Memoirs (1823), p. lxi.; F. Arago, _Analyse historique, Annuaire du Bureau des Longitudes_ (1842), p. 249; Arago, _Biographies of Scientific Men_, p. 167; Madame d'Arblay's _Diary, passim; Public Characters_ (1798-1799), p. 384 (with portrait); J. Sime, _William Herschel and his Work_ (1900). Herschel's photometric Star Catalogues were discussed and reduced by E. C. Pickering in _Harvard Annals_, vols. xiv. p. 345, xxiii. p. 185, and xxiv. (C. P.; A. M. C.)