[Letter] 1813 Feb, Camborne [to] Robt. Fox Junr./Richard Trevithick. 2p. on 1 leaf. [Describes a trial of boring limestone, with detailed results; estimates likely output of "the engine at Hayle" when used for limestone cutting. In postscript: has sent to John Gould an estimate for an engine etc "for clearing mud from Falmouth Harbour".]