Forty-seven letters, 1830-1846, from James Watt [1769-1848] of Birmingham and Doldowlod House, Radnorshire to William Mylne [1734-1790] and Robert Mylne [1733-1811], London. They relate to the making of machinery, to alternations made by Watt at Doldowlod House, and to the activities of surveyors employed by a company desirous of constructing a railway through part of Watt's property.