Chapter XVIII: Part 18

THE EARTH'S CENTER.--All bodies weigh less the further removed they are from the center of the earth. A block of stone weighing 700 pounds upon the sea-shore, will weigh only 699 pounds if carried up a mountain three miles high. A pendulum oscillates more quickly at the poles than at the equator, because the earth is flatter by twenty-six miles at the poles--that is, the "bob" of the pendulum is that much nearer the earth's center, and therefore heavier, and so swings more quickly.