While handling and inspecting this carefully preserved sextant on a table at the David Rumsey Map Center, it was easy to forget the bitter winds and rocking decks which confronted marine astronomers trying to use such instruments to take celestial measurements at sea. William Bayly’s logbook from 1772 to 1774 describes how
fantastical sights of icebergs, whales, dolphins, penguins, and the Aurora Australis alternated with horrendous weather, including violent storms and snow, waves breaking over the decks, and poor visibility … strong gales & squally with a hollow trembling Sea
But perhaps sitting from this privileged position is befitting, since this sextant appears never to have been used.
Jesse Ramsden’s dividing engine massively reduced the labour involved in the production of the precision navigation instruments. It marked a sociotechnical solution to the long-standing problem of determining longitude at sea. The Ramsden sextant’s wide arc, reflecting mirror, and accurately engraved scale were marvels of precision engineering, capable of measuring celestial distances down to a sixtieth of a degree. Since it could be produced without artisanal competence, the sextant was far cheaper than its more technically advanced rival – the marine chronometer. And the sextant was a kind of social technology in another sense, too. It conveyed authority on ship, to maintain the sense of hierarchy that prevented disorder or mutiny. Yet the luxurious nature and pristine condition of this sextant indicates it was never purchased for use in navigation or social coordination at sea. It seems rather to have been intended as a show piece, standing as it does for Britain’s rising coalition of commerce, industry, and genteel science, defenders and prime movers of the late eighteenth-century empire.(more…)