in navigation, an instrument consisting of two parts, which are two circles either laid one upon or let into the other, and so fastened together in their centres, that they represent two compasses, one fixed, the other moveable; each of them divided into the thirty-two points of the compass, and three hundred and sixty degrees, and numbered both ways, from the north and the south, ending at the east and west, in ninety degrees.

The fixed compass represents the horizon, in which the north and all the other points of the compass are fixed and immovable.

The moveable compass represents the mariners compass, in which the north and all other points are liable to variation.

In the centre of the moveable compass is fastened a silk thread, long enough to reach the outside of the fixed compass. But, if the instrument be made of wood, there is an index instead of the thread.

Its use is to find the variation of the compass, to rectify the course at sea; having the amplitude or azimuth given.

in the distillery, the person whose employment it is to take the coarse malt-spirit of the malt-stiller, and redilute it to a finer and better liquor.