| RefNo | Title | Date |
| MS/377/1/166 | Draft paper on entoptic vision by William Fletcher Barrett | no date |
| MS/377/1/158 | Sketch of optical apparatus by William Fletcher Barrett | no date |
| MS/377/1/160 | Notes on the eye by William Fletcher Barrett | no date |
| MM/14/164 | Letter from Assistant Secretary, Royal Society, to Alfred W Ewing | 6 November 1953 |
| MS/377/1/162 | Notes on the eye by William Fletcher Barrett | 24 January 1906 |
| MS/377/1/161 | Notes on the eye by William Fletcher Barrett | no date |
| MS/377/1/159 | Notes on books by William Fletcher Barrett | no date |
| MS/377/1/153 | Draft article by William Fletcher Barrett, 'Remiscences of Sir Robert Ball' | [1913] |
| MS/377/1/163 | Notes on experiments on the legibility of light by William Fletcher Barrett | 2 September-23 September 1909 |
| MS/377/1/152 | Draft letter from William Fletcher Barrett to the Editor of the Physical Review | [1922] |
| MS/377/1/164 | Experimental curve for light extinction experiments by William Fletcher Barrett | 6 September 1909 |
| MS/377/1/165 | Experimental curve for light extinction experiments by William Fletcher Barrett | 10 September 1909 |
| MS/743/1/79 | Letter from William Fletcher Barrett, Isleworth, to [John Hall] Gladstone | 18 June 1872 |
| MS/743/1/151 | Letter from William Fletcher Barrett, 6 De Vesci Terrace, Kingstown, Co Dublin, to [John Hall] Gladstone | 28 September 1893 |
| NLB/40/475 | Copy letter from Robert William Frederick Harrison to The Manager, Royal Bank of Ireland, Kingstown | 11 June 1909 |
| NLB/18/690 | Copy letter from Robert William Frederick Harrison, to Professor W F Barrett | 24 April 1899 |
| NLB/23/1/640 | Copy letter from Robert William Frederick Harrison, to Professor William Fletcher Barrett, Fellow of the Royal Society | 19 December 1901 |
| NLB/23/1/653 | Copy letter from Joseph Larmor, to Professor William Fletcher Barrett, Fellow of the Royal Society | 20 December 1901 |
| NLB/23/1/626 | Copy letter from Joseph Larmor, to Professor William Fletcher Barnett, Fellow of the Royal Society | 16 December 1901 |
| NLB/27/851 | Copy letter from Robert William Frederick Harrison, to Professor William Fletcher Barrett, Fellow of the Royal Society | 11 December 1903 |
| NLB/30/202 | Copy letter from Robert William Frederick Harrison, to Professor William Fletcher Barrett, Fellow of the Royal Society, 6 De Vesci Terrace, Kingstown | 13 February 1905 |
| NLB/28/503 | Copy letter from Robert William Frederick Harrison, to Professor William Fletcher Barrett, Fellow of the Royal Society | 21 March 1904 |
| NLB/31/30 | Copy letter from Robert William Frederick Harrison, to Professor William Fletcher Barrett, Fellow of the Royal Society | 9 June 1905 |
| NLB/32/449 | Copy letter from Robert William Frederick Harrison, to Professor William Fletcher Barrett, Fellow of the Royal Society, 6 De Vesci Terrace, Kingstown, County Dublin | 8 March 1906 |
| NLB/35/35 | Copy letter from Robert William Frederick Harrison, to Professor William Fletcher Barrett, 6 De Vesci Terrace, Kingstown, County Dublin | [8 April 1907] |
| NLB/32/787 | Copy letter from Robert William Frederick Harrison, to Professor William Fletcher Barrett, Fellow of the Royal Society, 6 De Vesci Terrace, Kingstown, County Dublin | 25 May 1906 |
| NLB/33/600 | Copy letter from Robert William Frederick Harrison, to Professor William Fletcher Barrett, Fellow of the Royal Society | 8 October 1906 |
| NLB/36/855 | Copy letter from Robert William Frederick Harrison, to Professor William Fletcher Barrett, Fellow of the Royal Society, 6 De Vesci Terrace, Kingstown, Dublin | 3 January 1908 |
| NLB/40/407 | Copy letter from Robert William Frederick Harrison to Professor W [William] F [Fletcher] Barrett FRS | 3 June 1909 |
| NLB/46/67 | Copy letter from Robert William Frederick Harrison, to Sir William Fletcher Barrett, Fellow of the Royal Society | 5 June 1912 |
| NLB/46/45 | Copy letter from Robert William Frederick Harrison, to Sir William Frederick Barrett, Fellow of the Royal Society | 3 June 1912 |
| NLB/46/303 | Copy letter from Robert William Frederick Harrison, to Sir William Barrett, Fellow of the Royal Society | 9 July 1912 |
| NLB/52/626 | Copy letter from Robert William Frederick Harrison, Assistant Secretary of the Royal Society; to Messrs Harrison & Sons | 31 January 1916 |
| NLB/52/206 | Copy letter from Robert William Frederick Harrison, Assistant Secretary of the Royal Society; to Sir William Fletcher Barrett, FRS | 14 October 1915 |
| NLB/52/266 | Copy letter from Robert William Frederick Harrison, Assistant Secretary of the Royal Society; to Sir William Fletcher Barrett, FRS | 27 October 1915 |
| NLB/54/3 | Copy letter from Robert William Frederick Harrison, Assistant Secretary of the Royal Society; to Sir William [Fletcher] Barrett, FRS | 11 January 1917 |
| MS/929/1/17 | Letter from William Fletcher Barrett, FRS, to James Mackenzie Davidson | 1910 |
| MS/929/1/18 | Letter from William Fletcher Barrett, FRS, to James Mackenzie Davidson | 5 February 1909 |
| MS/929/1/16 | Letter from William Fletcher Barrett, FRS, to James Mackenzie Davidson | 6 December [1909] |
| MS/929/1/15 | Letter from William Fletcher Barrett, FRS, to James Mackenzie Davidson | 10 February 1909 |
| NLB/68/138 | Copy letter from Francis Alexander Towle, Assistant Secretary of the Royal Society; to Sir William Barrett, FRS | 19 May 1925 |
| NLB/68/276 | Copy letter from Charles Scott Sherrington, President of the Royal Society; to Lady Barrett | 11 June 1925 |
| NLB/47/39 | Copy letter from Robert William Frederick Harrison to Sir William Barrett FRS | 19 November 1912 |
| NLB/27/810 | Copy letter from Joseph Larmor, to Professor William Fletcher Barrett, Fellow of the Royal Society | 3 December 1903 |
| EC/1899/02 | Barrett, William Fletcher: certificate of election to the Royal Society | |
| IM/000267 | Barrett, William Fletcher | 1922 |
| MS/377 | Collected papers of William Fletcher Barrett | 1863-1924 |
| NLB/52 | New Letter Book volume 52, copy letters sent from Royal Society administration | 9 July 1915-8 March 1916 |
| MC/19/43 | Letter from [William Fletcher Barrett], Royal College of Science, St Stepehen's Green, East, Dublin, to the Royal Society | 26 February 1904 |
| MC/19 | Volume 19 of miscellaneous correspondence regarding business matters, sent to the Royal Society | 1904 |