8 EABLY HISTORY OF THE NAUTICAL ALMANAC. 



satellite had been made before 1740 by Dr. Halley with the 

 mural quadrant at the Royal Observatory, and that lunar tables 

 had been formed by him and others ; but it was not till after the 

 publication in 1752 of his astronomical tables for computing the 

 places of the sun and moon, prepared by him before he became 

 Astronomer Eoyal in 1720, that the residual errors, determined 

 from a comparison of these lunar tables with the Greenwich 

 meridional observations of the moon, made between 1722 and 

 1739, were found to be far too great for the tables to be of much 

 practical value for the determination of the longitude at sea, 

 though they were in advance of others that had preceded them. 

 It is probable, therefore, that the "Nautical Almanac" would 

 not have been established even in 1767, had not more accurate 

 tables been constructed by Prof. Mayer, of Gottingen, founded 

 on the more recent observations. Fortunately, in 1765, Prof. 

 Mayer transmitted his tables in manuscript to Dr. Bradley, who 

 deemed them to be so accurate that, by using the calculated places 

 of the moon, they might serve in finding the longitude at sea 

 within half a degree of the truth, and generally much nearer. 

 After the death of Mayer in 1762, these manuscript tables were 

 placed in the hands of Dr. Maskelyne, who also considered them 

 sufficiently accurate for general nautical purposes, and by him 

 they were laid before the Board of Longitude as a work of both 

 scientific and national importance.* 



Before, however, the tables of Mayer could be made practi- 

 cally available, even when printed, it was necessary that some 

 means should be found to obviate the difficulty that would be 

 experienced at sea on account of the intricate calculations 

 required to obtain accurate tabular places of the sun and moon, 



*The " Board of Longitude " was formed by the Uovernment for the encour- 

 agement of nautical science, and especially of the problem of finding the longitude 

 at sea, by instituting rewards to such person or persons as shall discover a method 

 for finding the same, or shall make useful discoveries in navigation. The 

 " Nautical Almanac " owes its existence to a memorial presented to the Com- 

 missioners of Longitude by Dr. Maskelyne, on February 9, 1765, in which he 

 stated many facts and experiments to prove the utility of determining the longi- 

 tude at sea by the lunar method. On his recommendation the Board resolved 

 that an application should be made to Government to grant a reward to the 

 representatives of Mayer for his tables ; and " also for power to give a reward 

 to persons to compile a nautical ephemeris, and for authority to print the same, 

 when compiled, in order to make the said lunar tables of general utility." 



