MACKAY, Andrew.

Inquire · Offered by Peter Harrington

The Theory and Practice of Finding the Longitude at Sea: to which are added, Various Methods of determining the Latitude of a Place, and Variation of the Compass; with New Tables. First editions of these two works illustrating theory and business in the world of practical navigation in the late 18th century. Andrew Mackay (1758-1809) and John Hamilton Moore (1738-1807) built parallel careers as teachers of practical navigation, publishing widely used guides during a period when Harrison's chronometer vied with rival methods for determining longitude, especially lunar-distance measurements and observations of Jupiter's moons. Mackay's Theory and Practice surveys all these methods, drawing on his extensive personal experience: as keeper of the University of Aberdeen's observatory, he was able to observe the orbits of Jupiter's moons closely, while his duties included rating the latest crop of marine chronometers. The subscribers' list attests to his contemporary reputation, including such luminaries as Joseph Banks, Lord Monboddo, and William Herschel. Hamilton Moore combined his navigational teaching with a career as a mapmaker, building on his experience in the Royal Navy. In 1798, he was charged with pirating a chart by William Heather, his former assistant, who alleged that Moore, in his efforts to avoid copyright by adapting Heather's chart, had left out many dangerous rocks and shoals. The prosecution, led by Thomas Erskine, won the day.

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