Since first hearing of Newcastle born Charles Hutton in 2014, I have been chasing the history of a line.
It was invented 400 years ago, or perhaps only 250; depending on whether isobaths (the submarine version of contour lines) count.
Each time contour lines were invented it was in response to a particular problem which required a (visual) solution – on a map. The inventors were rarely cartographers, more often mathematicians, or polymaths, a connecting theme actually being an interest in meteorology.
Maps are usually drawn to define boundaries, often for defence or attack; or they are drawn for travellers, or landowners wanting to quantify what they possess. These maps are filled with symbols that represent things visible in that landscape: woods and windmills, roads, rivers, bridges and mountain ranges.
The maps explored here were the first to include those tentative lines that expose a quality of our world needing to be understood, to be calculated or defined, through the use of a line or lines which are not visible within the landscape.