How intrepid Victorian surveyors mapped the length and breadth of Britain

Reflecting worries that the French might invade, the first OS maps cover the mouth of the river Thames. This is the naval route to London and a highly vulnerable part of the country.

The sheets that follow stretch along the south coast: Dorset, Devon and on to Cornwall. These areas were similarly vulnerable to a French naval attack.

In the Bristol Channel the sheet for Lundy Island was delayed because, embarrassingly, it was surveyed by a trainee who put Lundy in the wrong place. The island had to be resurveyed and the map’s copper printing plate planed and re-engraved.

As they worked through Wales, the English-speaking surveyors struggled with Welsh place names, mangling many. Croeswdig was mapped as “Crosswoodig”, Rhos-y-cribed as “Rosey cribelt”.

OS developed a system for determining how place names should be spelled. This included checking with reputable members of the community. Landowners and the clergy were considered reliable. Small farmers and crofters were not, even if they had deep roots in an area.

The French threat had not been forgotten. A spot on the coast near Fishguard in Wales, mapped in 1819, is marked: “about 1000 Frenchmen landed here in 1797”, memorialising an attempted invasion.

OS’s path sweeps steadily northwards. Lincolnshire, though, was surveyed early and out of order. Excited at the prospect of showing off maps of their estates, landowners in the county offered to buy 500 maps if prioritised. They may have come to regret this: OS was still finding its feet and errors crept in. The results were, as the head of OS at the time put it, “slovenly”.

The prospect of invasion had receded by the middle of the century. Mapping in England paused in the 1840s. This was because the surveyors were shipped to Ireland to produce accurate maps for land taxation.

In Scotland surveying commenced in 1843 (the year The Economist was first published). The survey swept from south-west to north-east over time.

The Isle of Lewis in the Outer Hebrides was mapped out of sequence. James Matheson, who owned all of Lewis, paid OS to map it early. He made a case that he needed the maps to make agricultural improvements on his land.

The pace of the Industrial Revolution—with new railway lines, growing urban centres and sites of industry—made maps out of date even before they had been engraved onto copper plates for printing. Survey progress slowed as OS was distracted updating sheets.

West of London, for example, we can compare two versions of the same map. To keep up with the railways, mapmakers sometimes engraved new railway lines straight over the top of existing designs. Moving elements engraved on a metal plate is hard. The new lines run through the map labels.

This wasn’t the only challenge the railways posed. During “railway mania”, rapidly expanding rail companies poached surveyors from OS: almost 300 staff left in 1845.

As its work progressed, OS found new audiences. The Poor Law Commission was concerned with sanitary conditions in crowded cities. It commissioned maps for places like Manchester at a much larger cartographic scale with street-level detail. OS progress slowed as surveyors were occupied with other assignments.

In Scotland, delays caused by a dispute over the choice of cartographic scale and a lack of funds and staff were compounded by difficult Highland terrain and weather. Surveyors might be encamped on a mountain for weeks waiting for the mist to break. Tents were blown away, and surveyors complained of having to survive on porridge.

Field surveying was limited to the spring and summer. Unfortunately this overlapped with deer-stalking season. The survey clashed with Highland deer-forest proprietors who did not want surveyors on their land.

The final Scottish maps, of Orkney and Shetland, were published in 1882, eight decades after the project began with the first maps of Kent.