rule discovered by Mr Thomas Baker, whereby to find the centre of a circle designed to cut the parabola in as many points, as an equation to be constructed hath real roots. Its principal use is in the construction of equations, and he has applied it with good success as far as biquadratics.

The central rule is chiefly founded on this property of the parabola, that if a line be inscribed in that curve perpendicular to any diameter, a rectangle formed of the segments of the inscript, is equal to the rectangle of the intercepted diameter and parameter of the axis.

The central rule has the advantage over Cartes and De Latere's methods of constructing equations, in that both these are subject to the trouble of preparing the equation, by taking away the second term.

Centrifugal force, that force by which all bodies that move round any other body in a curve endeavour to fly off from the axis of their motion in a tangent to the periphery of the curve, and that in every point of it. See Mechanics.

Centrina, in ichthyology, the trivial name of a species of squalus. See Squalus.

Centripetal force, that force by which a body is everywhere impelled, or anyhow tends towards some point as a centre. See Mechanics.