Modus opticæ delineationis, absque lineis occultis.
_In hac figura sexta, vestigium geometricum ~B~ seorsim posui ab
elevatione geometrica ~A~, ut deinceps faciemus. Vestigium ~B~ opticè
contractum in ~E~ est ~NMRS~; elevatio contracta longitudinis vestigii
est ~FTSN~. Posito autem quòd altitudines ~FN~, ~1, 5~, ~2, 6~, sint
æquales; latitudines ~NM~, ~1, 2~, ~5, 6~, sint æquales; & rectæ ~NM~,
~5,6~, sint in linea ~X~ plani; rectæ ~FN~, ~1, 5~, sint in perpendiculo
~V~: anguli ~3~ & ~4~ basis ~C~ habent eandem elevationem seu distantiam
à linea ~X~ plani, quam habet angulus ~T~: anguli ~1~ & ~2~ habent
elevationem, quam angulus ~F~: anguli ~3~ & ~7~ habent eandem latitudinem
seu distantiam à perpendiculo ~V~, quam habet angulus ~R~: anguli ~2~ &
~6~ habent eandem latitudinem, quam habet angulus ~M~._
The Sixth Figure.
_The Manner of designing in Perspective, without occult Lines._
In this sixth Figure, I have design’d the Geometrical Plan B separately
from the Geometrical Elevation A, as I shall always do hereafter. The
Plan B optically contracted, or put in Perspective, in E, is NMRS; the
Elevation of its Length in Perspective is FTSN. Then supposing the
Heights FN, 1,5, 2,6, equal; and the Breadths NM, 1,2, 5,6, equal; the
Lines NM, 5,6, to be in the Line of the Plan X; and the Lines FN, 1,5, in
the Perpendicular V: the Angles 3 and 4 of the Base C have the very same
Elevation or Distance from the Line of the Plan X, as has the Angle T:
the Angles 1 and 2 have the same Elevation with the Angle F: the Angles 3
and 7 have the same Breadth or Distance from the Perpendicular V, as the
Angle R has: the Angles 2 and 6 have the same Breadth, as the Angle M has.
[Illustration: FIG. VII.]