The earliest map visited on my travels is of a navigation channel for the Spaarne by Pieter Bruins, Bruinsz or Bruinszoon in 1584. The dotted line marked ‘7 voet’ probably denotes water ‘deeper than’ and as such I consider it neither contour nor isobath (though the map is very lovely indeed). It’s unlikely that my personal shining star Pierre Ancelin knew of it when he invented isobaths over 100 years later. Information on him is hard to come by, there’s every chance he was a Huguenot, an article I have says he was ‘trained in France’ before going to work as ‘Town Surveyor’ in Rotterdam. Picked for his knowledge of water systems and the use of dams and other methods to reposition water flows, his contract was to create a series of scientific maps so the town elders could take effective measures to avoid the sanding up of channels. His employers were happy with the results, because his temporary contract was made permanent in 1698.How do I know this much? For each pocket of knowledge – as with ideas and inventions – there appears to me to be a ‘chain of custody’: David Fairbairn (Newcastle University) recommended visiting Peter van der Krogt (Amsterdam University), who in turn gave me an article about Ancelin written by Bertus Woude… in Dutch. I looked at the pictures and recognised dates, places and the odd word. Then whilst on mini-residency at VARC I happened to mention the article to friend and local resident Jan Ashdown who put me in touch with sheep farmer Peter Samsom who, being Dutch and shortly to embark on a long train journey, was happy to be given some diverting reading matter. A week later I met him in the Rocky Road Café where he managed a very elegant synopsis of Woude’s 19 pages over a pot of tea. There are probably easier ways of doing research, I like this way.
Certain books on cartography from the 1980’s suggest it was the Italian Luigi Marsigli who invented Isobaths, and indeed he did! (Around 10 years after Ancelin). So Ancelin and Marsigli both – independently – invented Isobaths; Nicolaus (Kruik or) Cruquius did not, although he claims to have done: it is clear he had seen Ancelin’s beautiful manuscript maps and also met with Marsigli on his visit to Holland. Cruquius ‘popularised’ isobaths, he was the first to promote the idea of them, and he wrote extensively on ‘his’ invention, but that actual ‘light-bulb’ moment was not his to claim.
I’m not even sure how important it is to be ‘first’ to think something; perhaps Cruquius is just as important as the disseminator of an idea: how to convey height or depth with a line.
Then there’s that giant step, or leap, out of the water; how to survey for and accurately position a line of equal altitude on dry land… or mountainside.
Did our Charles Hutton ‘invent’ Contour Lines without prior knowledge of Isobaths? It’s possible Henry Cavendish (who most certainly knew of them) tipped him the nod, I’d love to know. So Tuesday I’m away to Cambridge University Library to have a dig about in the Royal Greenwich Observatory’s archives, perhaps there’s a notebook, librarian or indeed a sheep farmer who can throw some light on my quest.
With kind acknowledgements to the Hoogheemraadschap van Rijnland, Rotterdam Stadsarchief and Leiden University for access to their archives and permission to use the photographs here.