which the English Government had offered for an instrument that should enable the longitude to be more accurately determined by navigators at sea than was then possible; and it was with the object of obtaining pecuniary assistance to assist him in completing his chronometer that Harrison had, in 1728, made his first visit to London to exhibit his drawings.
The Act of Parliament offering this superb reward was passed in 1714, fourteen years before, but no attempt had been made to claim it.

It was right that England, then rapidly advancing to the first position as a commercial nation, should make every effort to render navigation less hazardous.

Before correct chronometers were invented, or good lunar tables were prepared,[7] the ship, when fairly at sea, out of sight of land, and battling with the winds and tides, was in a measure lost.

No method existed for accurately ascertaining the longitude.

The ship might be out of its course for one or two hundred miles, for anything that the navigator knew; and only the wreck of his ship on some unknown coast told of the mistake that he had made in his reckoning.
It may here be mentioned that it was comparatively easy to determine the latitude of a ship at sea every day when the sun was visible.