omplicated
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 between the end proposed in the construction of the
building, 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 necessary 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 which it has acquired from experience,
and must see with the eye of childhood, no further than the surface.
Every person, who is accustomed to drawing in perspective, sees
external nature, when he pleases, merely as a picture: this habit
contributes much to form a taste for the fine arts; it may, however,
be carried to excess. There are improvers who prefer the most dreary
ruin to an elegant and convenient mansion, and who prefer a blasted
stump to the glorious foliage of the oak.

Perspective is not, however, recommended merely as a means of
improving the taste, but as it is useful in facilitating the knowledge
of mechanics. When once children are familiarly acquainted with
perspective, and with the representations of machines by elevations,
sections, &c. prints will supply them with an extensive variety of
information; and when they see real machines, their structure and uses
will be easily comprehended. The noise, the seeming confusion, and the
size of several machines, make it difficult to comprehend and combine
their various parts, without much time, and repeated examination; the
reduced size of prints lays the whole at once before the eye, and
tends to facilitate not only comprehension, but contrivance. Whoever
can delineate progressively as he invents, saves much labour, much
time, and the hazard of confusion. Various contrivances have been
employed to facilitate drawing in perspective, as may be seen in
"Cabinet de Servier, Memoires of the French Academy, Philosophical
Transactions, and lately in the Repertory of Arts." The following is
simple, cheap, and _portable_.

PLATE 1. FIG. 1.

A B C, three mahogany boards, two, four, and six inches long, and of
the same breadth respectively, so as to double in the manner
represented.

PLATE 1. FIG. 2.

The part A is screwed, or