DOI Page / Citation link:
https://doi.org/10.11588/diglit.18826#0153
110
ON PERSPECTIVE. [LECT. III.
PLATE XXXVIII.
IN THESE EXAMPLES, THE SUN IS BEHIND THE PICTURE.
H L is the horizontal line; C the center: fup-
pofed to be out of the picture immediately above L
(as may be found by tracing the radial lines) is the
place of the fun, confequently L is its tranfpofed
feat on the horizontal plane.
No. I. Is a cube with one face parallel to the pic-
ture: 1 is the fhadow of A, 2 of B, 3 of D; as
BD vanifhes in C, fo does its fhadow 2 3, being
parallel to it.
No. II. Explains the fhadow of a crofs: thefeatfrrf
of the crofs-beam (B D) is found by letting fall per-
pendiculars which are cut by a line from C, through
the bottom of the crofs. Radials are ruled from the
principal parts, as A, B, D; and interfered by
lines from L, through the feats of thofe parts, as
I, 2, 3, &c.
No. III. Shews the paffag-e of the fhadow over a
block lying along; the block vanifhes in C; the line
defcribing its further fide at bottom, being drawn,
the fhadow of the crofs is traced to it, it mounts
directly up that fide, and appears again on the fur-
face, where it recovers its former courfe. The
fhadow of the end of the block, at 4, 5, is found by
the fame method as in No. I.
No. IV. Is a cube, whofe fhadow is found by
ruling, from the place of the luminary, lines through
its upper corners, as a b; which are interfered by
lines from its lower corners drawn to L, as 1 L,
2 L: this fhadow, 1. 2. being parallel to the fide
a by tends to the vanifhing point of that fide.
No. V. To find the fhadow of a cylinder, felecr.
three or four points in its upper furface, abed;
find their feats at the lower furface, by letting fall
perpendiculars; rule radial lines, from the upper
furface: and from L, the feat of the luminary, rule
through the correfponding points below, till they
interfeci the former, as 1 2 3 4: unite thefe care-
fully to complete the figure.
PLATE
ON PERSPECTIVE. [LECT. III.
PLATE XXXVIII.
IN THESE EXAMPLES, THE SUN IS BEHIND THE PICTURE.
H L is the horizontal line; C the center: fup-
pofed to be out of the picture immediately above L
(as may be found by tracing the radial lines) is the
place of the fun, confequently L is its tranfpofed
feat on the horizontal plane.
No. I. Is a cube with one face parallel to the pic-
ture: 1 is the fhadow of A, 2 of B, 3 of D; as
BD vanifhes in C, fo does its fhadow 2 3, being
parallel to it.
No. II. Explains the fhadow of a crofs: thefeatfrrf
of the crofs-beam (B D) is found by letting fall per-
pendiculars which are cut by a line from C, through
the bottom of the crofs. Radials are ruled from the
principal parts, as A, B, D; and interfered by
lines from L, through the feats of thofe parts, as
I, 2, 3, &c.
No. III. Shews the paffag-e of the fhadow over a
block lying along; the block vanifhes in C; the line
defcribing its further fide at bottom, being drawn,
the fhadow of the crofs is traced to it, it mounts
directly up that fide, and appears again on the fur-
face, where it recovers its former courfe. The
fhadow of the end of the block, at 4, 5, is found by
the fame method as in No. I.
No. IV. Is a cube, whofe fhadow is found by
ruling, from the place of the luminary, lines through
its upper corners, as a b; which are interfered by
lines from its lower corners drawn to L, as 1 L,
2 L: this fhadow, 1. 2. being parallel to the fide
a by tends to the vanifhing point of that fide.
No. V. To find the fhadow of a cylinder, felecr.
three or four points in its upper furface, abed;
find their feats at the lower furface, by letting fall
perpendiculars; rule radial lines, from the upper
furface: and from L, the feat of the luminary, rule
through the correfponding points below, till they
interfeci the former, as 1 2 3 4: unite thefe care-
fully to complete the figure.
PLATE