As soon as he had obtained the post of Astronomer Royal, he began to call the attention of the Commissioners of Longitude to the practicability of the method of lunar distances, and proposed to them to establish a Nautical Almanac, which should contain such an ephemeris of the moon’s path as would make the object in view attainable. The memorial on this subject was presented February 9, 1765, and the evidence of various officers of the East India Company’s service was taken as to the success of the method. The lunar tables of Mayer furnished the proposed materials for the moon’s places; and upon the adoption of the scheme of Maskelyne, a parliamentary reward of 3000_l._ was given to Mayer’s widow. To Maskelyne we are thus indebted for a work which has more than any other contributed to the advancement of navigation, in the removal of the great difficulty of finding the longitude. It is true that this first effort could hardly then be expected to give the longitude within a degree; but this was a great improvement, when it is considered that the reckoning of a ship might be out several degrees, and that chronometers had not yet been introduced. But the ‘Nautical Almanac’ must be considered as a work addressed to astronomers as well as seamen, from its earliest commencement. Maskelyne saw the importance of saving the observer the trouble and risk of error which would attend his reductions without such assistance, and contemplated the continual improvement of the lunar tables. It is not one of the least obligations which astronomical science owes to Maskelyne, that since his time a very slender portion of mathematical knowledge will enable a diligent observer to turn his means to good account in the promotion of sidereal and even of planetary astronomy. Without saying that the observer, as such, is employed about the highest department of the science, or in any way recommending the lover of observation to stop his career at that point, we may remind him that, with the assistance of an ephemeris, such as the ‘Nautical Almanac’ of Maskelyne did, still more as that of the present day, he can never want the means of turning his amusements to useful purpose. The first Nautical Almanac was published in 1767, and was continued by Maskelyne to the end of his life. The requisite tables, intended to accompany that work, were first published by him in 1781.