Page:An Essay on the Life and Genius of Samuel Johnson.djvu/79

 the longitude, and was thought to have made great advances towards that important discovery. His letters to lord Halifax, and the lords of the admiralty, partly corrected and partly written by Dr. Johnson, are still extant in the hands of Mr. Nichols. We there find Dr. Williams, in the eighty-third year of his age, stating, that he had prepared an instrument, which might be called an epitome or miniature of the terraqueous globe, showing, with the assistance of tables, constructed by himself, the variations of the magnetic needle, and ascertaining the longitude, for the safety of navigation. It appears that this scheme had been referred to sir Isaac Newton; but that great philosopher excusing himself on account of his advanced age, all applications were useless, till 1751, when the subject was referred, by order of lord Anson, to Dr. Bradley, the celebrated professor of astronomy. His report was unfavourable, though it allows that a considerable progress had been made. Dr. Williams, after all his labour and expense, died in a short time after, a melancholy instance of unrewarded merit. His