199 
Description of the Optigraph* 
shall find some of the parts larger than in the other; both 
cannot be right: yet supposing them perfectly the 
same^ neither may be conformable to nature* In ad- 
dition to this, many situations of an object occur, which 
no eye, however habituated, can represent with accu- 
racy. 
On this account many attempts and various instruments 
have been made for the purpose of giving the outline of 
an object with accuracy. 
The late most ingenious Mr. Hams den, so well known 
for his inventions and improvements in various instru- 
ments, considered the present subject an object worthy 
of his attention, and invented the instrument I am about 
to describe, which is so simple and easy in its opera- 
tion, that a person not possessed of the least knowledge 
of drawing, may, with less than three minutes 5 instruc- 
tion, be perfectly able to take a perspective view of land- 
scape, building, machinery, or, in fact, an object of any 
description presented to his eye, with the utmost correct- 
ness. 
Mr. Hams den left this instrument without the means 
of enabling the operator to enlarge or diminish his draw- 
ing; an inconvenience which I have obviated, while at 
the same time I have added some other trifling improve- 
ments. This instrument is certainly superior to any hi- 
therto constructed for the same purpose ; for in this the 
operator views the object through a telescope, which ena- 
bles. him to delineate minute objects with great exactness 
and ease, which are often too far from the eye to be seen 
sufficiently well to be delineated correctly. 
Fig. 3, (plate 6,) is a perspective view of the opti~ 
graph. A represents the drawing board, on the outside 
frame of which is fixed the pillar of the instrument, B, by 
a clamp a . C is a tube, (sliding in the pillar,) on the 
top of which is fixed, by means of a screw c, the frame 
