Francis Lancaster who died in 1824 was a respected maker of Chronometers one of which can be found at the National Maritime Museum in London. The grave photograph has been sent to the museum by Ned
Francis, who had his workshop in Liverpool, is buried in Windleshaw Chantry along with his wife, Prudence. In 2005 Christie's of London LISTED THE FOLLOWING
LOT 247
Francis Lancaster. An 18ct Gold Open Faced Chronometer Watch
SIGNED FRANS LANCASTER, LIVERPOOL, NO 570, CHESTER HALLMARK FOR 1805
57mm
ESTIMATE
£1,800 - £2,500
($3,164 - $4,395)
PRICE REALIZED
£3,360
It's relatively easy to calculate latitude - your distance north or south of the Equator - by measuring the position of the heavenly bodies. But those alone won't let you calculate longitude - your position east or west. The answer to that problem turned out to be an accurate clock - a chronometer. Before a ship set sail, its chronometer would be set to the local time in harbour - for the British this was usually Greenwich. Once at sea, you could then compare the time at Greenwich with the time on board ship, wherever you were, which you could tell by the sun. And the difference between the two times gave you your longitude.
BBC - A History Of The World in 100 Objects ep 91