Robson, William: Grammigraphia; or the Grammar of Drawing. (London, 1799)

104

APPEARANCE,

N° II.

JL/ET the Gate be open to the dots 2 on the Step.

Examine, in the Gate and the Step, the difference between Reality
and Appearance, and compare them with

SITUATION 4.
parallel tottfj t&c CJettical ami ®toum platted

RULE. — They vanish in the Point of Sight.

// has Five Variations.

The Figures which refer to the Figures in Position are
also the Situation and Variation.

1 On the Ground Plane, as 4.1, and all the Positions on

the Step, except 4.5.

2 Above the Ground Plane, 4 • 3> on the Gate.

3 On the Horizontal Plane, 4.2, ditto.

4 Above the Horizontal Plane, 4 . 4, ditto.

5 On the Perpendicular Plane, 4.5, on the Step.
In the Point of Sight this Si-
tuation becomes a Point, as

in Position, No. IV. 4 . 6, the center Bar of the

Gate.

The Parallels of this Situation are, it will be seen, always parallel
with each other, and all are parallel with the Vertical and Ground
Planes. But in Appearance they are never parallel with each other;
and none can be parallel with the Vertical Plane. Their appear-
ance is, Oblique to it, upon it, and on the Horizontal, forming
the three Positions, Perpendicular, Horizontal, and Oblique.