Liquid compass
Bowl: White metal, set in an outer anti-vibrational bowl, diameter 6.25" (16.9cm). Inside of bowl painted grey. A centesimal scale graduated to 100 degrees is fitted in fore side of bowl. The 50 degree mark corresponds with the fore and aft line. Verge glass is painted over with black paint only leaving clear a quadrant allowing the scale and card to be seen.
Card: Wire spider of four elements and has a very small card at centre showing four points, marked in white 0, 1, 2, & 3. These are placed so that the angular distance betwen the 0 and 1, 1 and 2, 2 and 3 is 100 degs in each instance, the distance between the 3 and 0 being 60 degrees. So the course to steer is north. No 3 pointer is made to coincide with 60 dgrees on the scale, and the course is therefore either 360 degrees or 0.