Here is another one of my blog entries for the Transit of Venus project:
Out of the Diaries: 17 January 1761
On 17 January 1761 Nevil Maskelyne and his assistant sailed to St Helena to view the transit there – one of the few observation locations in the Southern hemisphere and therefore an important counterpart to those in the far north. St Helena was a lone speck of land in the South Atlantic and had been in the possession of the British East India Company for nearly a century. It was an important stopover on their trading route and Maskelyne was hitching a ride on an East Indiaman.
The twenty-seven-year-old Maskelyne was a curate in Chipping Barnet, a small town to the north-west of London, but he seemed to have preferred astronomy to the Bible. Maskelyne had been a fellow of the Royal Society for a few years and had volunteered to sail to St Helena. Not only had he made sure to have the best instruments but he also managed to receive a very generous liquor allowance – the bill for wine and spirits accounted for almost one-quarter of the entire budget for the expedition.
Maskelyne’s ship was accompanied by several heavily armed vessels which were sailing to the West Indies. At the Canary Islands the convoy turned west while Maskelyne’s ship continued south. During those long weeks on board he tested his lunar method of determining longitude at sea. Night after night, Maskelyne peered through his telescope, measuring the moon’s path across a tapestry of fixed stars. Page upon page, he scribbled his observations and calculations in his note book. ‘My principal attention on board’, Maskelyne later told the Royal Society, was ‘to be satisfied … of the practicability of that method’. There was only one problem with his lunar method: it involved such complicated calculations that sailors couldn’t glance quickly into the sky to work out their longitude. Each of the calculations was so complex that the whole process took around four hours, which was no problem for Maskelyne who adored lists and order.
But it was not all hard work on board ship. Traveling with more than one hundred gallons of wine and rum as well as five gallons of spirits and over seventy bottles of claret, Maskelyne noted that it was ‘a very agreeable voyage’.