  We consider the Center of Gravity of a solid, partly filled with some
homogeneous material, and find its qualitative and quantitative properties. In
particular, we prove that the Center of Gravity has its lowest position when it
lies on the top surface of the material inside the solid and find a
differential equation for the first moments that explains this result in both
mathematical and physics terms. We make explicit calculations of this lowest
position in a number of cases, such as cylinders, cones, solids of revolution,
power solids, spheres and half spheres.
