in *Geometry*, any line which is neither straight nor composed of straight lines; or, in other words, a line of which no three consecutive points are in the same straight line.

**Curve of Equable Approach**. Leibnitz first proposed to find a curve down which a body descending by the force of gravity shall make equal approaches to the horizon in equal portions of time. This curve, as it has been found by Bernoulli and others, is the second cubical parabola placed with its vertex uppermost, and which the descending body must enter with a certain determinate velocity. The question was rendered general by Varignon for any law of gravity, by which a body may approach towards a given point by equal spaces in equal times. Maupertuis also resolved the problem in the case of a body descending in a medium the resistance of which is as the square of the velocity.

**Curves, Algebraical or Geometrical**, are those in which the relation of the abscisses to the ordinates can be expressed by a common algebraic equation.

**Curves, Transcendental or Mechanical**, are those which cannot be defined or expressed by an algebraic equation.