MARINER'S Compass. See COMPASS.
The invention of the compass is usually ascribed to Flavio da Meli, or Flavio Gioia, a Neapolitan, about the year 1302; and hence it is, that the territory of Principato, which makes part of the kingdom of Naples, where he was born, has a compass for its arms. Others say that Marcus Paulus, a Venetian, making a journey to China, brought back the invention with him in 1260. What confirms this conjecture is, that
at first they used the compass in the same manner as the Chinese still do; i. e. they let it float on a little piece of cork, instead of suspending it on a pivot. It is added, that their emperor Chiningus, a celebrated astrologer, had a knowledge of it 1120 years before Christ. The Chinese only divide their compass into 24 points. Fauchette relates some verses of Guyot de Provence, who lived in France about the year 1200, which seem to make mention of the compass under the name of marinette, or mariner's stone; which shew it to have been used in France near 100 years before either the Melsite or Venetian. The French even lay claim to the invention, from the fleur de lys wherewith all nations still distinguish the north point of the card. With as much reason Dr Wallis ascribes it to the English, from its name compass, by which name most nations call it, and which he observes is used in many parts of England to signify a circle.
The compass hath sometimes been observed to be disturbed by the electricity of its glass-cover; and this from so slight an application of the finger as was barely necessary to wipe off a little dust. The same glass, rubbed a little more with the finger, a bit of muslin, or paper, would attract either end of the needle, so as to hold it to the glass for several minutes, far out of the due direction, according to that part of the glass which was most excited. And when the needle, after adhering to the glass, has dropped loose, and made vibrations, those would not be benefited as usual by that point where the needle should rest, but would either be made all on one side, or be very unequally divided, by means of some remains of electrical virtue in that part of the glass which had attracted the needle, until at length, after 15 minutes or more, all the electricity being discharged, the magnetical power took place. The remedy for this inconvenience is to moisten the surface of the glass: a wet finger will do it immediately and effectually. The mariner's compass with a chart is much less dangerously moved than the common compass with a bare needle: and the deeper, or farther distant, the needle hangs below the glass, the less disturbance it is likely to receive.