Jackson, Frank G · London : Chapman & Hall · leaf 237
rly themeasurements of Angles by Arcs of Circles and the construction of the Scale ofChords. These Set Squares afford unlimited scope for right-lined exercises, i.e.drawing parallel lines at fixed distances, angles of any number of degrees—Square,Oblong, Pentagon, Hexagon, &c, &c, without… … BLACKBOARD SET. 7s. 6d. Consisting of 3-feet Flat (Reg.) Blackboard Ruler and ExtraLarge Patent 450 and 6o° Set Squares. The Blackboard Ruler is made of the finest seasoned Boxwood, painted withblack lines over the divisions, figures, Sec, and the Scales used are the same asmarked on 9-inch Flat…
Decoration and ornament
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