Worthen, William Ezra, 1819-1897, [from old catalog] ed · New York, Appleton · leaf 57
e of one of therulers being retained in a position coinciding with, or parallel to, a given line,when the other ruler is moved, lines drawn along its edge are also parallel tothe given line. This instrument is only useful in drawing small parallels, andin accuracy and convenience does not compare… … Fig. 122. connected by an axle passing under the metal cover, ^, Z>, and revolving in. thesupports, c, c ; the wheels come slightly below the surface of the wood, asshown in the end elevation. In drawing parallel lines the fingers are placedwith a firm pressure about the centre of the metal…
Mechanical drawing
Internet Archive · Library of Congress · Public Domain Mark 1.0. Free to use for anything.
![An illustration from [Graphophone patents] (1878)](https://img.insideoutlibrary.com/img/200/ia-graphophonepaten10unit-641-439.webp)