The Artist's Repository, Or, Encyclopedia of the Fine Arts (Band 2): Perspective, Architecture (London, 1808)

LECT. II.J ON PERSPECTIVE

79

PLATE XXX.

INCLINED PLANES ON INCLINED PLANES.

Figure 1, Reprefents a prifm (one of whofe fides
is perpendicular to the ground) refting on an in-
clined plane: this figure is an advance on Plate
XXVIII. C is the center of H L, the horizontal
line; Z is the original plane, and Y the prifm (land-
ing on it. Draw through C, a line perpendicular to
it, as V C O : place the priim Y at the point of dif-
tance H, and rule lines equal to the angles it makes^
to O and to V j through thefe points, O and V, draw
lines parallel to H L, which thus become vanifhing
lines to its upper and under faces. The upper
faces of Z and Y being parallel, have the fame va-
nifhing point (O). The plane B, Figure 1, follows
exactly No. 2. Plate XXVIII. take g h for the feat
ofAonB; from V draw V g, V h, beyond g and h;
and by the diagonal Ng prolonged beyond g, cutting
V h in b, we obtain one termination of this face*
which is completed by ruling a b parallel to gh.
Now rule for the other face a O, bO> which, cut
by the diagonal b K, will give edfov the termination
of the oiher face \ or> it may be found; by erecting a
perpendicular from g to c, and drawing c d. ef on.
the ground line marks the width of A.

In Figure 2, the plane A is cOnftructed in a fimilar.
manner with B in Figure Leg vanifhes in V ; and
f denotes the middle of the object: abed is a
fquare lying oblique to A; whofe fides a 6, and d d
vanifn in K: and ac and bd vanifh in a cor-
refponding point on the other fide O.

l 2 PLATE