Tra′cing-in′stru-ment.
An instrument for copying figures on an enlarged or reduced scale.
Its principle is the same as that of the profile-machine.
A long straight arm and a shorter curved arm have a universal-joint movement about a common point.
The longer arm being passed over the outlines of an object, the shorter arm, which is provided with a pencil or tracer, produces a copy on a smaller scale, upon a sheet held in proper position to receive it; or the functions of the two may be reversed, producing an enlarged copy.
The
silhouette instrument is similar.