Huw Thomas, Map Curator at The National Library of Wales takes part in our #LoveMaps Campaign.
The Ordnance Survey Six-Inch Maps
Being a Map Curator one sees a large number of maps of all different varieties, but there are few map series which match the Ordnance Survey Six-inch maps either for their continued usefulness or their aesthetic appeal.
The use of the six-inch scale goes back to the very beginnings of the OS when some of the early surveys were carried out at this scale. In 1824 it was adopted as the survey scale for the survey of Ireland and the success of this led to it being used for surveys in Great Britain. In 1854 when it was decided to survey cultivated areas at the 25-inch scale the six-inch scale was still retained for uncultivated areas, but regardless of the survey scale all areas were published at the 6-inch scale as well.
The earliest published sheets at this scale were engraved full sheets such as this example of Pembrokeshire sheet XXXIX originally published in 1869. The fine detail of the engraving of these maps makes them some of the most beautiful maps ever produced by the OS; however, by this time engraving on copper plates was beginning to be superseded by more cost effective methods of printing.
From the 1880s onwards most of the six-inch maps were produced using a process called photo-zincography, a printing method pioneered by the Ordnance Survey which allowed them to produce maps much more cheaply. The sheets were now published as quarter sheets such as the second map shown here, Pembrokeshire XX.NE published in 1891.
Although the photozincographed quarter sheets lack the fine detail of the engraved full sheets they are still items of beauty in their own right and in one aspect improve on the engravings in that the water features are coloured blue. As photozincography was not a colour printing process the blue was added by hand by boys employed at the Ordnance Survey Office in Southampton.
Beyond their aesthetic appeal the six-inch maps are still proving useful today, in my work I use them on an almost daily basis for the valuable information they provide about the historical landscape.
Looking at the content of the maps, it can be seen that the first shows part of Milford Haven and includes the town of Pembroke Dock. Pembroke Dock owes its existence to the Royal Naval Dockyard built at the site; it was for this reason that Southern Pembrokeshire was the first part of Wales to be mapped by the original Ordnance Survey in 1809-10 and also the first part to be mapped on the 6-inch scale starting in 1860.
On closer examination one curious feature of the map can be seen, the naval dockyard is shown as a blank white area. It was common practice for the OS not to show military establishments and other sensitive locations, a practice which continued until the 1990s.
If the first map was chosen to show one of the earliest areas to be mapped the second was chosen instead for its location. Today is March the First, the feast of St David and this map shows the City and Cathedral which bear his name.
Dydd Gŵyl Dewi Hapus!
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