Finding longitude at sea had long been a concern for navigators. Chronometers, first devised by John Harrison in the mid-1700s, kept a record of time at the Royal Observatory, Greenwich. When navigators compared this with local time at sea, determined from observations of the Sun or stars, they were able to find their longitude. John Arnold was one of Britain’s leading makers of chronometers at the end of the 1700s.

Finding longitude at sea had long been a concern for navigators. Chronometers, first devised by John Harrison in the mid-1700s, kept a record of time at the Royal Observatory, Greenwich. When navigators compared this with local time at sea, determined from observations of the Sun or stars, they were able to find their longitude. John Arnold was one of Britain’s leading makers of chronometers at the end of the 1700s.

Finding longitude at sea had long been a concern for navigators. Chronometers, first devised by John Harrison in the mid-1700s, kept a record of time at the Royal Observatory, Greenwich. When navigators compared this with local time at sea, determined from observations of the Sun or stars, they were able to find their longitude. John Arnold was one of Britain’s leading makers of chronometers at the end of the 1700s.