The centre of gravity of any parallelogram lies on the straight line joining the middle points of opposite sides. Archimedes
It follows at once from the last proposition that the centre of gravity of any triangle is at the intersection of the lines drawn from any two angles to the middle points of the opposite sides respectively. Archimedes
The centre of gravity of any cylinder is the point of bisection of the axis. Archimedes
The centre of gravity of any hemisphere [is on the straight line which] is its axis, and divides the said straight line in such a way that the portion of it adjacent to the surface of the hemisphere has to the remaining portion the ratio which 5 has to 3. Archimedes
If two equal weights have not the same centre of gravity, the centre of gravity of both taken together is at the middle point of the line joining their centres of gravity. Archimedes
The times when the centre of gravity of political development and the crystallising agent of capitalist contradictions lay on the European continent, are long gone by. To-day Europe is only a link in the tangled chain of international connections and contradictions. Rosa Luxemburg