198 
Description of the Optigraph . 
Further experiments and observations, setting forth 
the advantages that electricians are likely to obtain 
from the above discovery, will be the subject of a future 
paper* 
NO. 89* 
Description of the Optigraph ( invented by the late Mr. 
Hamsden) as improved and made by Mr. Thomas 
Jones.* 
(With an engraving.) 
THE methods used to facilitate the practice of draw- 
ing in perspective, as well for those versed in this polite 
art, as for those who have made less proficiency, have 
been various and numerous. Though some have sup- 
posed that the warmth of imagination and luxuriance of 
fancy, which impel the mind to the cultivation of the fine 
arts, are not to be confined to mechanical modes, yet 
upon observation and inquiry they will find that the 
most able and accomplished artists are often obliged to 
have recourse to some rules, and to use some mechani- 
cal modes to guide and correct their pencil : but so te- 
dious is the operation, and great the difficulty, of repre- 
senting objects in true perspective, that they trust mostly 
to their eye and experience for success. The result of 
such a mode of proceeding may be determined by por- 
traits drawn by the best artists, and the different judg- 
ments formed concerning them. It has been well ob- 
served, that there is no artist who will be hardy enough 
to say that he can delineate by the eye the same object 
twice with exactness, and preserve a just and similar 
proportion of parts in each. In one of the figures we 
Tilloch,vol. 28, p. 66, 
