Image of Thomas Young Hall's adjustable coal screen from A Treatise on the Extent and Probable Duration of the Northern Coal Field, by T Y Hall, 1854. The original from which this has been scanned is in the North of England Institute of Mining and Mechanical Engineers. It is reference Tracts vol 39 p219 A. The scan and the upload to Wiki Commons have been made with the permission and direction of their librarian Jennifer Kelly. The original is fragile and this upload does not contain the accompanying textual description which can be consulted via the Institute.

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