*curtain*, or *courtin*, in fortification, is that part of the rampart of a place which is betwixt the flanks of two bastions, bordered with a parapet five feet high, behind which the soldiers stand to fire upon the covered way and into the moat.

**Curtius (Quintus)**, a Roman gentleman an Rom. 392. Understanding by the oracle, that a certain gulf in the forum, which boded misfortune to the city, could only be stopped by throwing the most precious thing they had into it; Curtius, considering of it, thought his own merit above all others, and leaped into the abyss, which (it is said) suddenly closed up.

**Curtius (Quintus)**, a Latin historian who wrote the Life of Alexander the Great in 10 books, of which the two first are not indeed extant, but are so well supplied by Freinshemius, that the loss is scarcely regretted. Where this writer was born, or even when he lived, are points no one pretends to know: by his style he is supposed to have lived in or near the Augustan age; while some are not wanting, who imagine the work to have been composed in Italy about 300 years ago, and the name of Quintus Curtius to be fictitiously added to it. Cardinal du Perron was so great an admirer of this work, as to declare one page of it to be worth 30 of Tacitus: yet M. le Clerc, at the end of his Art of Criticism, has charged the writer with great ignorance, and many contradictions.

**CURVATURE of a Line**, is the peculiar manner of its bending or flexure, by which it becomes a curve of such and such peculiar properties.