I was visiting the Intrepid museum in NYC (an aircraft museum housed in a retired aircraft carrier – a real treat!) and they had, as a bonus, a fifites-era submarine, the USS Growler, moored alongside the carrier. So I had to see that too (of course).

Submarines are always amazing from a design standpoint, given the intense constraints they have to accommodate. There were many complex pieces of machinery below deck, but one of them struck me with its simplciity. It was a “Ship clinometer, Type II – Heel”, and I snapped its photo for you.

Ship clinometer on submarine USS Growler

“Heel” is the inclination of a ship sideways, and this device tells the submariners how far their vessel is heeling away from the vertical. No need to explain how it works, of course… it’s a cousin of the humble (and equally useful) spirit level we have in our toolboxes. I imagine that today more sophisticated instruments exist, bristling with electronics and digital displays; but actually, this pair of curved glass tubes must’ve done just as good a job – the Growler carried nuclear missiles, and I’m sure its designers preferred its captain to know which way was up…