A well-known formula enables us to compute the velocity a body would acquire in falling from an infinite distance to the earth or any other planet whose size and force of gravity are known.

The same formula, taken in the opposite sense, of course, shows how fast a body must start from a planet in order that it may be freed from its control.

The formula is V = square root of (2 gr.), in which "g" is the acceleration of gravity, equal for the earth to 32 feet in a second, and "r" is the radius of the attracting body.

On Menippe I knew "g" must equal about one twentieth of a foot, and "r" 31,680 feet.

Like a flash I applied the formula while the giant's muscles were yet tightening for the kick: 31,680 x 1/20 x 2 = 3,168, the square root of which is a fraction more than 56.