Mirtus or Metius, a Roman youth, who, in B.C. 362, devoted himself to death for the safety of his country. A wide chasm having suddenly opened in the Forum, the oracle declared that it never would close until Rome threw into it whatever she accounted her greatest treasure. Curtius immediately perceived that an armed citizen was the sacrifice required; and having armed himself and mounted his charger, he plunged into the abyss, on which the earth instantly closed over his head.

Curtius, Rufus Quintus, the celebrated biographer of Alexander the Great. Of his personal history nothing whatever is known with certainty, some fixing his epoch in the Augustan, others as far down as the mediæval age. It is, however, more probable that he flourished somewhere during the first three centuries of the Christian era. His work originally consisted of ten books, but the first two of these are entirely lost, and the remaining eight present considerable gaps. The supplements of Freinsheim are the most valuable; and the best modern editions of the text are those of Zumpt, Bamstark and Mittzell.

**CURVATURE OF A LINE**, is the peculiar manner of its bending or flexure, by which it becomes a curve of such and such form and properties. Thus the nature of the curvature of a circle is such that every point in the periphery is equally distant from a point within called the centre, and hence the curvature of the circle is everywhere the same; but the curvature in all other curves is continually varying.