Sheet 42sw, Old Series 1". 1873. First edition, late issue. Glamorganshire: Brecon Beacons, Dowlais. Hand-coloured engraving
Sheet 42sw, Old Series 1". 1873. First edition, late issue. Glamorganshire: Brecon Beacons, Dowlais in SE corner. Hand-coloured engraving, 45 x 61cm. Base map 1832, pre-railway, geology not dated although geologists named as typical for earliest geological maps, issued 1873. Flat , clear plate mark, full margins, slightly age-toned, clean, colours bright. Minor marginal tears to side margins. Engraving skewed on sheet. Neatly drawn in by hand, the course of the River Taf Fawr and three then proposed reservoirs, which now exist. Stencilled no in lower left corner. In good condition.
About the England & Wales One Inch Old Series
The Geological Survey of England and Wales used the Old Series of the Ordnance Survey topographic map at a scale of one inch to the mile as its basemap, initially. These engraved basemaps were published and revised between 1805 and 1885; the sheet sizes varied and the layout and numbering system were eccentric. The Old Series geological maps were hand-coloured and without geological sections, which were published separately. The GS of E&W published the Old Series from 1850 to 1900, when it switched to the colour printing and the New Series one inch maps. However, old stock of the Old Series continued to be issued, hand-coloured, until the 1930s.