Pendulum the pendulum could be used to measure the force of gravity. During his expedition to Cayenne, French Guiana in 1671, Jean Richer found that a pendulum clock was minutes per day slower at Cayenne than at Paris. From this he deduced that the force of gravity was lower at Cayenne. In 1687, Isaac Newton in "Principia Mathematica" showed that this was because the Earth was not a true sphere but slightly oblate (flattened at the poles) from the effect of centrifugal force due to its rotation, causing gravity to increase with latitude. Portable pendulums began to be taken on voyages
Paraconical pendulum about its vertical axis as well as swinging in two perpendicular directions. Therefore a paraconical pendulum has three degrees of freedom. When the rotation of the Earth is taken into account, the formal equations in classical mechanics of the behavior of this dynamical system are rather complex. The rolling friction of the ball upon the flat is extremely low, so that a paraconical pendulum has a high Q factor, principally determined by air resistance. Typically a paraconical pendulum is built as a solid body with a stiff rod, rather than with a flexible wire or cord, and its length is