Perspectographs by George Adams
From Inventions
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Inventor
George Adams Jr. (1750-1795)
Historic Period
1791
Description
Two instruments for perspective drawing invented by the English mathematical instrument maker George Adams Jr. According to Adams, the novelty of these two instruments is that “The object is delineated on a horizontal plane, the pencil B, may be moved in any direction, whether curved or straight, with the utmost freedom.” In other words, both instruments, unlike its mechanical predecessors since Cigoli’s perspectograph, allowed the draughtsman to use direct contour drawing, by simply moving the pencil, in which turn activated the cursor (sight) that was used to survey the object or landscape and traced it into an image. Presumably, both Adams devices do not seem to be as effective as the author advocated. Their first problem is related to the difference in resistance of the two complex mechanisms used to move the pencil and the sight simultaneously in compliance: to move vertically the sight in the first machine (Fig. 1, Plate XXXII), Adams adopts a cable, two pulleys, a spring and two ‘pantographs’ attached at right angles; to move the same sight horizontally he uses only four casters, fitted in the groove that serves the crossbeam that supports the machine. The two casters next to the the pencil and under the horizontal ‘pantograph’ can be moved in any direction and help keeping the mechanism leveled and stable, regardless of the direction in which it is moved while drawing. The larger caster in the backround of the machine goes into action only when the mecanism is moved laterally. In Adam’s second device (Fig. 2, Plate XXXII), although he employes a different mechanical solution, there is also a considerable gap between the resistence of the two mechanisms used to move the cursor vertically and horizontally. Even if the prototypes were refinedly calibrated, it is legitimate to have some doubts on these machines efficiency and on how the pencil could actually be moved freely and with the same smoothness in any direction. In theoretical terms it would be possible to adopt a contour drawing, but perhaps more practical and accurate would be to use less sophisticated machines, such as the ones proposed a few years before by Johan Gabriel Doppelmayr (1677-1750), in Nicolas Bion’s Neueröfnete matematische Werkschule, or by James Watt (1736-1819) and James Lind (1716-1794), in Martin Benjamin’s Principles of Perspective, in which both machines the image would be obtained dot by dot. To our knowledge no drawings have survived made with the two Adams spectacular mechanisms, probably because Francis Ronald’s (1788-1873) perspectograph, followed by Charles Gavard (1794-1871) and Adrien Gavard of Paris diagraphes would in turn be lighter, more portable and efficient. On the other hand, it is known that in this period the camera obscura was the most popular drawing device, and curiously, just a few years later, around 1806 or even before, William Hyde Wollaston (1766-1828) would patent the camera lucida, the most efficient and popular capturing device invented before the discovery of the chemical process that would lead to photography. In fact, the camera obscura and camera lucida have another significant advantage over all the mechanical drawing apparatus ever invented: they would enable, although in different ways and through different principles, the juxtaposition of the object and the image to be traced.
Bibliographical Resources
Adams, George. Geometrical and Graphical Essays, Containing a General Description of the Mathematical Instruments Used in Geometry, Civil and Military Surveying, Levelling and Perspective, with many new Practical Problems. London, 1803 (1st edition 1791), pp. 458-460 and Plate XXXII.
Kemp, Martin. The Science of Art. Optical themes in Western Art from Brunelleschi to Seurat. New Haven and London: Yale University Press, 1990, pp. 187-189.
Cabezas, Lino. Las máquinas de dibujar. Entre el mito de la visión objetiva y la ciencia de la representación. In: MOLINA, Juan J. G. (Edit.). Máquinas y Herramientas de Dibujo. Madrid: Ed. Cátedra, 2002, p. 233.
Images
George adams perspectographs.jpg
George Adams Jr. (1750-1795), perspective instruments, Geometrical and Graphical Essays..., 1791). |
Author of the entry: Pedro Maia
