Prof. Watuace on the Invention of the Pantograph. 419 
the original. Of these, a sheet of semi-transparent tracing paper 
laid on the subject to be copied, is one of the most simple and 
elegant. On this, the engraver may make an outline of a subject 
which he means to transfer to his copperplate. If he set no va- 
lue on the original design, he may dispense with the transparent 
paper; and having made a trace with black lead along the lines 
to be copied, he may render them visible on the copper by the 
pressure of the rolling-press. 
Another elegant way of making a copy is by means of a tra- 
cing glass. This, fixed in a frame, is placed in a sloping direc- 
tion like a writing desk: the sheet to be copied is laid on the 
glass, and the paper on which the copy is to be made above it: 
a strong light, either natural or artificial, is directed upwards 
through the glass, while the surface on which the copy is to be 
made is skreened from the light. The lines to be copied are 
thus made visible through the two sheets, and a trace is made on 
the uppermost by carrying a point over them. 
If a subject is to be diminished or enlarged, none of these 
methods will apply. Now this is by far the most common case 
at the present time, when numberless Encyclopedias, Atlases, 
and other works illustrated by figures, are in progress of publica- 
tion, the materials of which are, for the most part, taken from 
writers of established eminence. 
It may be supposed that attempts must long ago have been 
made to furnish the various classes of artists with instrumental 
aid. Jn investigating this subject, however, I did not find that 
the mechanical contrivances for copying on an enlarged or redu- 
ced scale, had been numerous or considerably different, or that 
their application can be traced to a very remote period. There 
is a well known instrument called the Panrocrapu : this appear- 
ing to have been the earliest, and that from which all the others 
have been imitated, I was induced to look into its history ; I 
found it figured and described by various writers, who yet have 
given no indication of its inventor. In a work called “ Geome- 
VOL. XIII. PART I. 3H 
