Aliud exemplum vestigii geometrici, cum elevatione longitudinis.
_Si delineanda sit basis dissecta in quatuor partes, fiat vestigium ~A~
cum suis divisionibus longitudinis ~ED~ & latitudinis ~CD~. Easdem vero
divisiones latitudinis habebit in ~EF~ elevatio ~B~ quæ pertingit usque
ad ~X~. Porro ad contractionem opticam vestigii adhibebitur papyrus
complicata in latum & in longum, transferendo in lineam plani latitudinem
& longitudinem vestigii. Deinde nullo negotio fiet optica deformatio
elevationis, ut clarè positum est in figura. Quomodo autem ex vestigio &
ex elevatione longitudinis opticè imminutis eruatur basis nitida sine
lineis occultis, ex præcedentibus manifestum est. Optarem ut per assiduam
circini tractationem in hac methodo exercenda operam sedulò ponas; quum
ex ea pendeat omnis facilitas delineationum opticarum._
The Seventh Figure.
_Another Example of a Geometrical Plan and Upright, put in Perspective._
For drawing in Perspective a Pedestal, or Base, divided into four Parts,
make the Plan A with its Divisions of Length ED, and of Breadth CD;
and the same Divisions of Breadth EF, in the Elevation B, prolong’d
to X. Then make the Perspective-Plan, by transferring the Breadth and
Length into the Ground-line, by means of your Paper folded cross-wise.
From which Plan the Perspective-Upright is very easily made, as may
be plainly seen in the Figure. How the Base below, without occult
Lines, is made from the Perspective-Plan and Upright, is manifest from
what has been said before. I could wish you would be very diligent in
the Practice of this Method by the Compass; because the Dispatch of
Perspective-Delineations chiefly depends thereon.
[Illustration: FIG. 8.]