The artists repository and drawing magazine: exhibiting the principles of the polite arts in their various branches (3.1789)

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OBSERVATIONS,
Relating to the Examples given in the Plates, and which belong
to the foregoing Difcourfe.
ALTHOUGH geometry must not be permitted
precedence of some of the general principles of
perspedfive, yet is an acquaintance with certain of its
problems very useful to the sludent ■ principally for the
sollowing reasons (i) because, being formed by the com-
panies and ruler, they are mathematically exadt; and
therefore (2} They discover at a glance the disserence be-
tween the same figure in geometrical proportion,and when
seen in perspedtive: as for inslance, a square, or a circle,
is determinately different in its form and appearance. We
shall therefore attend somewhat to the simple elementary
figures of this science, and to the readied; methods of
forming them, previous to rendering them in perspedtive.
PLATE I.
No. I. Two lines not parallel,produced till they meet,
will form an angle: thus A and B are united at C,
.and form the angle ACB. N. B. An angle being
generally denoted by three letters, the middle one
always represents the angular point.
An angle is divided by setting one foot of the com-
passes on the angular point C, and striking the arch
' P E : then from D and E, svveeping E F, and D F ;
E 2 whose