Francis Henry Butler

“ Staunton, in vol. i. of his Embassy to China (London, 1797) , after referring to the early acquaintance of the Chinese with the property of the magnet to point southwards, remarks (p. 445) , “The nature and the cause of the qualities of the magnet have at all times been subjects of contemplation among the Chinese. The Chinese name for the compass is ting-nan-ching, or needle pointing to the south; and a distinguishing mark is fixed on the magnet’s southern pole, as in European compasses upon the northern one.” ”

“ They have no genius for Sea-voyages, and consequently are very raw and unexperienced in the art of Navigation, scarce venturing to sail out of sight of land. I speak of the natural Turks, who trade either into the black Sea or some part of the Morca, or between Constantinople and Alexandria, and not of the Pyrats of Barbary, who are for the most part Renegade s, and learnt their skill in Christendom The Turkish compass consists but of 8 points, the four Cardinal and the four Collateral. ”

“ To correct the heeling error, an adjustable magnet is applied below the compass in a line through its centre perpendicular to the deck. For taking bearings, a new instrument, the azimuth mirror, is provided, whereby the image of the object reflected from a plane mirror is thrown, as in a camera lucida, on the graduated circle of the compass card, and is seen through a convex lens. ”

“ We have already seen that the Chinese as -late as the end of the 18th century made
voyages with compasses on which but little reliance could be placed ; and it may perhaps be assumed that the compasses early used in the East were mostly too imperfect to be of much assistance to navigators, and were therefore often dispensed with on customary routes. The simple water-compass is said to have been used by the Coreans so late as the middle of the 18th century ”

“ Barlow reported to the Admiralty that half the compasses in the Royal Navy were mere lumber, and ought to be destroyed. Since then many improved varieties of ships compasses have been introduced, of which may be mentioned those of Pope, Preston, Walker, Dent, Stebbing, Gowland, Gray, Duchemin, and Harris. In the last the needle turns upon a point which is the centre of a doubly-curved bar of copper, fixed as a diameter to a ring of the same metal. In the Admiralty compass the bowl is of copper, the card of mica; and compound magnetic bars, as proposed by Scoresby, are employed.}}
Fig. ”

“ These instruments they have, from us, and made by our artists, and they do not in the least vary from ours, except that the characters are Arabic. The Arabs are the most skilful navigators of all the Asiatics or Africans ”

“ In those parts under the north are the mountains of loadstone, which give the virtue to the air of attracting iron ; but because it [the load stone] is far off, [it] wishes to have the help of a similar stone to make it [the virtue] work, and to direct the needle towards the star. [4] Brunetto Latini also makes reference to the compass in his encyclopaedia Livres dou tresor, composed about 1 260 ; and a letter written in 1269, attribiited to Peter Adsiger, shows that the declination of the needle had already been observed at that date. ”

“ A hemispherical space below the compass-case, nearly filled with castor-oil, serves to calm the vibrations of the bowl.
See articles Magnetism and Navigation; Cavallo, Treatise on Magnetism, 2d ed., Lond. 1800; Macpherson, Annals of Commerce, 1805; Airy, Phil. Trans., 1839, and 1846, part i., and Magnetism, sect, x., 1870; Johnson, On the Deviations of the Compass, 1852; Evans, Phil. Trans., 1860; Scoresby, The Compass in Iron Ships, 1855, &c.; Evans and Smith, The Admiralty Manual of the Compass; Merrifield, Magnetism and the Deviation of the Compass, part ii., 1872; Harris, Rud. Treat. ”

“ C, Box for corrector; a, Aluminium boss; b. Central cap of sapphire; c, Cords connecting rim and boss; d, Magnets e, Threads connecting magnets; f, Aluminium rim; f′, Cords supporting magnets; g.g′. Knife edges for gimbals. ”