On the lodestone and magnetic bodies and on the great magnet the earth : a new physiology demonstrated with many arguments and experiments / William Gilbert of Colchester, physician of London ... a translation by P. Fleury Mottelay.

  • Gilbert, William, 1544-1603.
Date:
1893
Catalogue details

Licence: Public Domain Mark

Credit: On the lodestone and magnetic bodies and on the great magnet the earth : a new physiology demonstrated with many arguments and experiments / William Gilbert of Colchester, physician of London ... a translation by P. Fleury Mottelay. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

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    found by means of a dip instrument even in the darkest night and in the thickest weather. Thus then, to bring our discourse back again to you, most worthy and learned Mr. Gilbert (whom I gladly acknowledge as my master in this magnetical philosophy), if these books of yours on the Loadstone contained nought save this one method of finding the latitude from the magnetic dip, now first pub- lished by you, even so our British mariners as well as the French, the Dutch, the Danes, whenever they have to enter the British sea or the strait of Gibraltar from the Atlantic Ocean, will justly hold them worth no small sum of gold.1 And that discovery of yours, that the entire globe is magnetical, albeit to many it will seem to the last degree paradoxical, never- theless is buttressed and confirmed by so many and so apposite experiments in Book II, Chapter XXXIV; Book III, Chap- ters IV and XII; and throughout nearly the whole of Book V, that no room is left for doubt or contradiction. I come therefore to the cause of magnetic variation—a problem that till now has perplexed the minds of the learned ; but no one ever set forth a cause more probable than the one proposed now for the first time in these your books on the Loadstone. The fact that the magnetic needle points due north in the middle of the ocean and in the heart of continents—or at least 1 Hardly twenty years after the English artificer, Robert Norman, had, in 1576, devised the inclinatoritim, which enabled him to determine the dip or inclination of the magnetic needle, Gilbert boasted that, by means of this in- strument, he could ascertain a ship's place in dark starless nights. Gilbert commends the method as applicable aire caliginoso; and Edward Knight, the English mathematician, in the introduction which he added to his master's great work, describes this proposal as worth much gold. Having fallen into the same error with Gilbert of presuming that the isoclinal lines coincided with the geographical parallel circles, and that the magnetic and geographical equa- tors were identical, he did not perceive that the proposed method had only a local and very limited application (Humboldt, Cosmos, 1849, Vol. I, page 172, and Vol. II, page 658). «