B60 Description of a Perspective Instrument . 
out and explain to them the first prints that they exa 
mine ; they may afterwards be left to themselves. 
“To understand points of machines, a previous know- 
ledge of what is meant by an elevation, a profile, a sec- 
tion, a perspective view, and a ( vue d/oiseau) bird’s eye 
view, is necessary. To obtain distinct ideas of sections, 
a few models of common furniture, as chests of drawers, 
bellows, grates, &c. may be provided, and cut asunder in 
different directions. Children easily comprehend this 
part of drawing, and its uses, which may be pointed out 
in books of architecture ; its application to the common 
business of life is so various and immediate, as to fix it 
for ever in the memory ; besides, the habit of abstraction, 
which is acquired by drawing the sections of compli- 
cated architecture or machinery, is highly advantageous 
to the mind. The parts which we wish to express are 
concealed, and are suggested partly by the elevation or 
profile of the figure, and partly by the connection be- 
tween the end proposed in the construction of the build- 
ing, machine, &c. and the means which are adapted to 
effect it. 
“A knowledge of perspective is to be acquired by an 
operation of the mind, directly opposite to what is neces- 
sary in delineating the sections of bodies ; the mind must 
here be intent only upon the objects that are delineated 
upon the retina, exactly what we see ; it must forget or 
suspend the knowledge it has acquired from experience, 
and must see with the eye of childhood no farther than 
the surface. Every person who is accustomed to draw 
in perspective, sees external nature, w hen he pleases, 
merely as a picture : this habit contributes much to form a 
taste for the fine arts ; it may, however, be carried to ex- 
cess. There are improvers who prefer the most dreary 
ruin to an elegant and convenient mansion, and who pre- 
fer a blasted stump to the glorious foliage of the oak. 
