Floating the Magnet.
--For some time past it has been found that there were great advantages in floating the magnetic index-card of a ship's compass on a liquid, instead of supporting it on a pivot. It has now been proposed by M. Santi, a manufacturer at Marseilles, to employ glycerine for this purpose. This succeeds admirably; the great oscillations caused in the compass-card by the vibration of the screw in steamers are almost.