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MACKAY, Andrew.

The Theory and Practice of Finding the Longitude at Sea or Land:

to which are added, various methods of determining the latitude of a place, and variation of the compass; with new tables.

London: for J. Sewell, P. Elmsly, and J. Evans, 1793 Stock Code: 119448
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First edition of this important and scarce work. The Scottish teacher of navigation, Andrew Mackay (1758-1809), "corrected the latitude of Aberdeen, estimated the longitude by comparing timings of Jovian satellite phenomena with Greenwich, and rated chronometers. Meantime he earned his living teaching mathematics, geography, navigation with lunars, surveying, and fortification" (ODNB) and the current work gained him the "thanks of the boards of longitude of England and France" (ibid.). In his Preface, Mackay makes an interesting reference to the horologists John Harrison, Larcum Kendal and John Arnold: "If a chronometer or timekeeper could be constructed, so as to go uniformly when placed in different position, and under different degrees of heat, then would this method of finding the longitude at sea be a most valuable acquisition to the navigator... every person acquainted with the principles of watchmaking must highly admire the accuracy of Harrison's timekeeper. Those made by Arnold and Kendal are also excellent; but it is to be hoped, that instruments of this kind may be still farther improved, and may be afforded much cheaper than at present, for the high price is a very great objection to them, and very much prevents their being generally used".

Inscribed in a contemporary hand on the front free endpaper: "J. Wallace. Two volumes in one vide Page 264"; possibly the author of A New Treatise on the Use of Globes and Practical Astronomy (New York 1812). With, below this, a presentation inscription (dated 1834) to a "Mr. W. M. C. K. P. Davies".

The list of subscribers runs to approximately 530 names (taking in the region of 610 copies) and is largely Scottish, predominantly from Mackay's home town of Aberdeen, listing many shipmasters, mathematical instrument makers, and merchants; it includes Sir Joseph Banks and the astronomers Nevil Maskelyne and William Herschel. Library Hub locates copies at 12 British and Irish institutional libraries; WorldCat adds a little over a dozen worldwide but this is very scarce in commerce, and only a handful of copies have appeared at public auction since 1966.

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2 volumes bound as one, octavo (211 x 126 mm). Recent half calf period style (retaining the original endpapers), red morocco label, marbled sides.


7 engraved folding plates.


Scattered foxing and a few old pale stains. A very good copy, with half-title to both volumes.


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