ABSTRACT
Late in 1837 De la Beche transferred the work o f the Geological Survey to south Wales partly to pursue economic geology by surveying its coalfield and partly to revive his interest in the complicated geology o f Pembrokeshire on which he had published a memoir and map in 1823. A basic responsibility o f the miniscule Survey was to colour geologically the one-inch-to-the-mile Ordnance Survey maps so that the main areas and boundaries o f different strata were shown. Having begun near Swansea in Glamorgan, De la Beche expanded his Survey westwards through Carmarthenshire into Pembrokeshire and its coalfield, and eastwards to the coal measures o f the eastern end o f the Mendip Hills, Bristol, and the Forest o f Dean. In 1842 the Survey pushed north o f the Forest to the Malvern Hills, which lay south o f the Bewdley coalfield near Kidderminster. By 1846 the Survey had issued geological maps which covered not only Cornwall and Devon but also five counties o f south Wales (Pembrokeshire, Carmarthenshire, Glamorgan, Brecknock, Monmouthshire) and parts o f Herefordshire, Gloucestershire, and Somerset. In the rubrics o f the maps De la Beche stressed that his Survey was mapping areas containing or bordering coal fields.
