Although several schemes had been projected, none of them had proved successful, and the offered rewards therefore still remained unclaimed.
To return to Harrison.

After reaching his home at Barrow, after his visit to London in 1728, he began his experiments for the construction of a marine chronometer.

The task was one of no small difficulty.

It was necessary to provide against irregularities arising from the motion of a ship at sea, and to obviate the effect of alternations of temperature in the machine itself, as well as the oil with which it was lubricated.

A thousand obstacles presented themselves, but they were not enough to deter Harrison from grappling with the work he had set himself to perform.
Every one knows the beautiful machinery of a timepiece, and the perfect tools required to produce such a machine.