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Account of the Invention of the Pantograph, and a Description of 

 the Eidograph, a Copying Instrument invented by William 

 Wallace, A. M., F. R. S. Edin., F. R. A. S., Memb. Cam. 

 Phil. Soc, &c, Professor of Mathematics in the University 

 of Edinburgh. 



{Read 13th January 1831.) 



The power of making such a representation of any object, as 

 shall give a distinct idea of its form, is a faculty which artists pos- 

 sess in different degrees of perfection. The principal difficulty 

 is, to get a first delineation of any subject ; from this a copy 

 may be made in various ways, with less exertion of talent than 

 was required for the composition of the original. 



Various geometrical and optical inventions have been pro- 

 posed to assist the artist in making an outline of an object which 

 he wishes to represent. The Reticulated Square and other con- 

 trivances, for placing every point of the thing to be represented 

 in its proper place in the picture, belong to the first class ; the 

 Camera Obscura and the Camera Lucida to the second. When 

 a design is to be copied, a different kind of contrivances will in 

 general be more convenient. It is only of these that I propose 

 to treat here. 



In making a copy, the assistance the artist seeks from mecha- 

 nical invention is, the power of forming a correct outline. In 

 many cases, as in the formation of maps and some architectural 

 designs, this is all that is wanted : the gradations of light and 

 shade must, in general, be given by the imitative skill which the 

 artist exerts by the eye alone. 



There are various well known contrivances by which a copy 

 of any design may be made, when it is to be exactly the size of 



