The biographies listed here include those of people whose work promoted the science of navigation. They are: Tobias Mayer (1723-1762), a German Professor, whose lunar and solar tables published in England in the 18th Century were good enough to determine longitude at sea with an accuracy of half a degree; John Hadley (1682-1744) who invented the sextant which measured the altitude of the Sun or a star above the horizon to find geographic positions at sea; Nevil Maskelyne (1732-1811) a British astronomer who experimented with the determination of longitude by observations of the Moon's position and introduced this method into navigation by publishing `The British Mariner's Guide' (1763). He published the first volume of the `Nautical Almanac' in 1766 and continued the supervision of the almanac until his death; John Flamsteed (1646-1719) founder of the Greenwich Observatory, and the first Astronomer Royal of England; and Jonas Moore (1627-1679) famous for his strong support of mathematics and astronomy which made many other mathematical and astronomical advances possible.