Egg diagram is used in the ice charts to represent the amount of ice in the area, types of ice and age of the ice in the are covered by the ice chart. It is called egg diagram because of the oval shape in which the diagram is represented. See "http://www.arcticclimatemodeling.org/lessons/acmp/acmp_58_SeaIce_CrackingTheEggCode.pdf" for explanation.
gyroscopic inertia and precession. either top heavy or bottom heavy, using mercury ballastics and precise weights to damp in drift and tilt to make it north seeking
