Correspondence with tradesmen, including letters from booksellers; coal merchants; clock repairers; horologists; builders; chandlers; merchants; instrument makers; opticians; parcel carriers; chemists; journeymen; decorators; bookbinders; the Post Office; gas engineers; newspapers; railway companies; and the Kent Water Company. The letters cover various instructions; requests; accounts; invoices; bills; receipts; tenders; circulars; routine repairs; and adjustments and improvements to instruments. There are also notes by W.H.M. Christie; experiments on spectroscopes; and two booklets on a patent stone preserver.