Augmentation

Chambers's Encyclopaedia, Volume 1: A to Beaufort, p. 569

Augmentation, in Music, is the reproduction of a melody, or principal subject of a composition, in the course of the progress of the piece, in notes of greater length than those notes in which the melody is first introduced. The tempo remains unaltered. Augmentation is of great importance in the treatment of the subjects, or themes, for fugues, and when cleverly used, produces great effects.

Source scan(s): p. 0592