Bronze Age Gold from Wales

Printed in black ink on off-white paper. Full title - 'Steam production at collieries. Where the life of a steam driven pit does not justify electrification, it is often possible to effect considerable economies by improved boiler plant, steam storage and similar modifications.' by E.Ivor David. Four pages held together by a pin. Includes several graphs and diagrams. A paper in Colliery Engineering, February 1950. Loose within a beige/light brown file with all other documents with the accession number 83.184I/70. The file is labeled 'Steam and Electric Collieries'.