"And at Greenwich Mason first learned to know Mayer's Tables of the Moon. ...Bradley first reported on Mayer's Tables on February 10, 1756, and finally on April 14, 1760. With the assistance of Charles Mason, Bradley had compared positions of the Moon as predicted in the Tables with positions as observed at Greenwich. Eleven hundred comparisons led to the comment: So far as it will depend upon the lunar tables the true longitude of a ship at sea may in all cases be found within about half a degree and generally much nearer. It remained to be examined within what limits the errors arising from observations actually taken at sea could be contained. This test was carried out for Bradley by Captain Campbell, of H.M.S. Royal George, on cruises near Ushant in 1758 and 1759. A sextant was made especially for the trials by John Bird, instrument maker for Greenwich Observatory. Bradley's final comment reads: However great the difficulties of finding the longitude by this method seem to be, they are not insuperable, or such as ought to deter those whom it most nearly concerns from attempting to remove them. James Bradley was now nearing the end of his days. His hand was faltering. Nevil Maskelyne and Charles Mason received the torch he had carried. They made the development of the method of lunar distances for finding the longitude at sea a major concern of the rest of their lives."