Optica projectio stylobatæ.
_Si libitum fuerit delineare stylobatam, cum projecturis in summo &
imo, incipies ab elevatione geometrica ~A~, ducendo occultas ad id
necessarias, tum versus perpendicularem ~L~, tum deorsum pro vestigio
geometrico ~B~, cujus distantiæ transferentur in spatium ~G~. Si mensuræ
longitudinis distent spatio ~C~ à mensuris latitudinis, vestigium
deformatum videbitur distare à linea ~K~ plani, quantum est idem spatium
~C~. In construenda optica elevatione ~D~, visuales ex punctis lineæ ~L~
dabunt lineas latitudinis; lineas vero altitudinis accipies ex lineis
vestigii contracti, ut in figura. In formando stylobata nitido ~EF~,
locum anguli ~H~ dabit concursus latitudinis ex linea ~L~ usque ad ~M~, &
altitudinis ex linea ~K~ usque ad ~I~. Concursus tum ejusdem altitudinis,
tum latitudinis ex ~L~ usque ad ~O~, dabit angulum ~N~. Demum altitudinem
anguli ~P~ accipies ex ~K~ usque ad ~Q~; latitudinem ex ~L~ usque ad ~R~._
The Eighth Figure.
_The Projection of a Pedestal in Perspective._
If you would draw a Pedestal, with the Projecture of its Cap and Base,
you must begin with the Geometrical Elevation A, by drawing such occult
Lines as are necessary, as well sideways to the Perpendicular L, as
downwards for making the Geometrical Plan B, whose Distances must be
transferr’d, and carry’d into the Space G. If the Measures of the Length
be placed the Distance of the Space C, from those of the Breadth, the
Perspective-Plan will then appear removed within the Ground-line K, as
much as the said Space C is. In the Construction of the Perspective
Elevation D, the Visuals drawn from the Points of the Line L give the
Lines of the Breadth; and those of the Height are taken from the Lines
of the Perspective-Plan, as in the Figure. In delineating the clean or
finish’d Pedestal EF, the Intersection of the Breadth from L to M, with
the Height from K to I, gives the precise Place of the Corner H. The
Intersection of the same Height with the Breadth LO gives the Angle N.
Lastly, the Angle P is found by the Intersection of the Height KQ, with
that of the Breadth LR.
[Illustration: FIG. IX.]