Double Parallel Ruler
From Inventions
Name adopted by the inventor.
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Inventor
Benjamin Martin (1705-1782)
Historic Period
1770
Description
Instrument for perspective drawing and reproducing drawings based on the mechanism of the parallel ruler, which in this case, doubled again, is called "double parallel ruler". The instrument consists of three horizontal rulers that remain parallel to one another, being connected to four small rods hinged to their ends. The lower ruler is fixed to the base of the stand supporting the drawing board with the sheet of paper. The middle ruler ensures that the horizontal rulers remain parallel to one another, while the upper ruler, carrying a sight, slides over the drawing paper. The sight is positioned at the top of a vertical rod fixed orthogonally the upper ruler at its midpoint. The painter, having established the viewing point, sights the distant points, intersects the visual ray with the sight and traces the resultant point on the paper at the base of the vertical rod. To reproduce a drawing on the same scale, the drawing is placed above the board, and the sight becomes an indicator of the various points to be transcribed.
Bibliographical Resources
Martin, Benjamin. The principles of perspective, London, 1770.
Images
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Author of the entry: Filippo Camerota
