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Account of the Invention of the Pantograph, and a Description of 
the Eidograph, a Copying Instrument invented by WiLL1aM 
Wa uace, 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.) 
Tue 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 
