Copy [letters] Apr 10/15, Leicester Square [to] Navy Commissioners/Lt.Col. J D'Arcy, late Royal Artillery. [As executor of the state of the late Charles Broderip, he is anxious to effect his wish that his country should benefit from his inventions. Copy letter, Apr 10, bears copy letter of 1820 Dec 5 to C Broderip/Capt. Geo. Harris, HMS Hussar; copy letter of Apr 15 bears long note by D'Arcy re 'Some of the properties of Mr Broderip's Marine Steam Engines briefly explained'. Broderip took our four patents between 1811 and 1821, including no.3506 (of 1811 Nov) and 4622 (of 1821 Dec), re steam engines]