Our Italian Marsigli has important friends; on Isaac Newton’s recommendation he had been elected a member of the Royal Society in 1691. In the 1720’s he visits London then travels on to the Netherlands where at Leiden he also met with Hermann Boerhaave (regarding his ‘flowering’ corals -among other sea specimens) and ‘s Gravesande who shared his interest in water flow. The visit also resulted in his (finally) finding publishers in Amsterdam for his Histoire Physique de la Mer. It’s unlikely his manuscript would have survived, so his trip was a success for us too in that we have – over the centuries – retained access to his thinking.
At this point our latest (and last) ‘man of the isobaths’ enters the scene. Nicolaus Cruquius was studying at Leiden University at the time of Marsigli’s visit, and although there are no records of direct acquaintance, he was studying with both Boerhaave and working directly on water flow with ‘s Gravesande so it is almost certain he would have encountered Marsigli’s isobath. In discussion with Dr Peter van der Krogt from Amsterdam University it is also pretty certain that Cruquius had seen Ancelin’s map(s) of Rotterdam.
To modern eyes a branching contour line looks (and is) wrong, but Cruquius (below) employs the same ‘mistake’ as Ancelin (right) – perhaps following his lead – they both draw bifurcating lines, often as a circle attached to a longer hoop, suggesting the depth and shape of an underwater feature is in doubt: either / or situations.
Cruquius is vital to my story (and will get his own ‘post’ shortly), unlike Ancelin and Marsigli, he never really dropped out of fashion, his remarkable printed maps are abundant, I have seen them at: the British Library, with thanks to Martijn Storms at Leiden University and as beautiful atlas versions courtesy of Peter van der Krogt at Amsterdam University (although the best online point of access is Utrecht University’s excellent copy).
Cruquius becomes a member of the Royal Society in 1724 and I do wonder if 50 years later another Royal Society member: Henry Cavendish, recalls seeing these cartographical wonders and tips the nod to our own Charles Hutton?… it’s a long shot.