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  Surveying Instrument Collection 


Troughton & Simms, London



Serial Number



Length 850mm, Diameter of base 120mm




This Eidograph is an mechanical plotting instrument used to redraw maps at a smaller or larger scale. It has the same function as a pantograph. It is a brass structure consisting of a round base 120 mm in diameter and a horizontal scale bar rests on the top of the base which may be adjusted to the required scale. There is a graduated disk located at each end of the bar allowing for smooth well-defined lines to be transferred to the other map. One of these disks feature a guiding pin which is to be guided along the lines on the map to be copied, and the other holds the plotting pin which plots the map at the new scale. Both ends of the scale bar are connected to each other via an enclosed string which acts like a 'pulley system'. When a line is traced from the original map with the guiding pin, this exact line is transferred via the disks and the string to the copied map by the plotting pin at either the same or different scales.

History & comments

The Eidograph was designed and published by an Edinburgh professor of mathematics, William Wallace. For reference see:

"Account of the Invention of the pantograph and a description of the eidograph, a copying instrument invented by William Wallace". Trans. of the Royal Society of Edinburgh 13 (1836), pp. 418-439

Simpson, A. D. C. 1991. 'An Edinburgh intrigue: Brewster's Society of Arts and the pantograph dispute', The Book of the Old Edingurgh Club, 1(1991), 47-73

Stanleys, W. F. "Mathematical Instruments"


Stored in a large wooden box (as seen in image)



  • Extra extension bars may be attached to the instrument if required
  • Instrument was donated by the Harbour and Roads Department of New South Wales
  • Inscription: 'Troughton & Simms London / Harbour & Roads Department N. S. W.' 
  • Many thanks to Stephen Johnston of the Museum of the History of Science in Oxford (3 January 2001) for providing the first two references on the Eidograph and for pointing out the error in the initial classification as 'planimeter'.
  • Many thanks to Dave Thompson (10 July 2004) for pointing out the same cataloguing error and for providing the third reference.
  • Catalogued by T. Ko
  • Updated by F. Pall and J. M. Rüeger (2005)


Manufactured in 1880 (approx). Catalogued in 1997 & 2005

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