There are various autograph letters written and received by Augustus de Morgan in the University of London Library. University College London holds correspondence and papers, 1827-1871 (Ref: MSS ADD 2-3, 5-7, 27, 69), correspondence with George Boole, [1842]-1864 (Ref: MS ADD 97), correspondence with Henry Peter Brougham, 1st Baron Brougham and Vaux (Ref: Brougham Papers), and letters to the Society for the Diffusion of Useful Knowledge, 1827-1844 (Ref: SDUK); the Royal Astronomical Society Library, London, has correspondence and papers, 1831-1866 (Ref: MSS de Morgan), and letters from De Morgan to the Society, 1831-1866 (Ref: RAS letters); the Royal Observatory Library, Edinburgh, contains a catalogue of mathematical books (Ref: NRA(S) 2657); the Bodleian Library, Oxford University, holds family correspondence (Ref: Dep Lovelace Byron), miscellaneous correspondence (Ref: MS Autogr d14), and correspondence with Anne Isabella Byron, Lady Byron (Ref: Dep Lovelace Byron); Cambridge University Library has correspondence with Sir George Biddell Airy, 1850-1870 (Ref: RGO MSS 942-52), letters to William Hepworth Dixon, 1856-1857 (Ref: Add 9428), and letters to William Thomson, Baron Kelvin, 1845-1849 (Ref: Add 7342, 7656); the British Library, London, contains correspondence with Charles Babbage, 1830-1850 (Ref: Add MSS 37185-200); the National Library of Scotland, Edinburgh, holds letters to Alexander Campbell Fraser, 1855-1864 (Ref: Dep 208); Edinburgh University Library has letters to James Orchard Halliwell-Phillipps, 1845-1851 (Ref: LOA); Trinity College, Dublin, contains letters to Sir William Rowan Hamilton, 1841-1865 (Ref: MS 1492); the Royal Society, London, holds correspondence with Sir John Frederick William Herschel, 1st Bt, 1831-1870 (Ref: HS), and letters to Sir John William Lubbock, 3rd Bt, 1832-1860 (Ref: LUB); Trinity College Library, Cambridge University, has letters to William Whewell, [1832]-1866 (Ref: Whewell MSS); the American Philosophical Society Library, Pennsylvania, USA, holds letters, 1841-1866 (Ref: NUC MS 76-902).