What A Relief! From Caterpillars to Contour Lines.

Actually, let’s start with mole hills. Traditionally, symbols on maps are derived from the natural world. If you want to show a wood, draw a bunch of trees, as simple as that. For about 300 years most map-makers elected to represent hills and mountains in profile, now referred to in the trade as the ‘mole hill’ or ‘sugarloaf’ model.

Our first image is one of the first attempts to show relief on a map, from an edition of Ptolemy’s Geographia first published in Rome in 1478 (the second ever printed book illustrated with maps). These mountains are supposedly to be found north of Crimea

Next, engraved c. 1610 (this edition 1676) John Speed depicts Plynlimon in profile. He certainly succeeds in demonstrating that it is the highest point in the Cambrian Mountains in mid Wales.

Joannes Blaeu’s engraving style is more flowing, but the idea is the same. Here is hilly country in northern Hertfordshire – note the beacon near Royston. This example was published in 1645.

In the late 18th century, just pre-Ordnance Survey, using hachures became more popular. Hachures are strokes drawn in rows in the direction of the slope, shorter and fatter where the slope is at its steepest and thinner and longer where it is more gentle. It’s certainly a step beyond drawing a picture, and the technique still in use today (for example showing railway cuttings or embankments on modern OS maps). Looking at the results, though, it is easy to see why hachured hills and mountains are dismissively referred to as ‘caterpillars’.

Like these caterpillars on the Cape: Aaron Arrowsmith uses hachuring on his scarce, separately published 1815 map of South Africa – one of the first detailed British maps of the region. And here's more hachuring on James Playfair’s 1821 map of Hindostan – a detail of hilly Nepal.

Contour lines were also devised in the 18th century, and were in widespread use by the 1840s. They are accurate and reliable (200 years later we are still using them), but gathering the data and preparing the map was time consuming and expensive. It is curious to think that this map of the North West Frontier of India was probably the most expensive map added to the second edition (1894) of Stanford's London Atlas. A British obsession with a potential Russian invasion via Afghanistan explains why this relatively remote area was treated in such lavish detail.