A Treatise of Artificial Magnets; in which is shewn an easy and expeditious method of making them, superior to the best natural ones: and also, a way of improving the natural ones, and of changing or converting their poles. Directions are likewise given for making the mariner’s needles in the best form, and for touching them most advantageously, &c.

Cambridge: Printed by J. Bentham… .1750

8vo, 1 leaf, 81 pages, 1 folding engraved plate. Contemporary half calf, spine gilt, red morocco label. Title slightly soiled, but a nice copy. Armorial bookplate of Sir Richard Bempde Johnstone, Bart.

FIRST EDITION. An important book by the eminent English scientist John Michell (1724–1793), in which he described the method of making artificial magnets by “double touch”, and enunciated the law of variation of magnetic action according to the inverse squares of distances. The formulation of this law is found on p. 19 and is reproduced in the Wheeler Gift catalogue (I, p. 188). Michell also did very important work in astronomy, invented the torsion balance for measuring very small forces, and may be said to have founded scientific seismology. Wheeler Gift 358. Ekelöf 320. Mottelay p. 191. With this copy is bound John Hill’s A Dissertation on Royal Societies (London, 1750), 48 pages.


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