Correspondence with tradesmen, including letters from booksellers; coal merchants; clock repairers; horologists; builders; merchants; draughtsmen; instrument makers; stationers; opticians; the Kent Water Company; engineers; chemists; a cloth maker; photographic suppliers; decorators; the Phoenix Gas Company; customs; printers; and journeymen. The letters cover instructions; requests; accounts; bills; receipts; circulars; tenders; invoices; routine repairs; and adjustments and improvements to instruments. There are letters from J. Glaisher, an extract on N. Arnott's ventilating valve, and a booklet on the advantages of gas lights in private houses.