Sheraton, Thomas; Bensley, Thomas; Mathews, James; Bensley, Thomas [Oth.]; Mathews, James [Oth.]; Terry, George [Oth.]; Jordan, Jeremiah Samuel [Oth.]; Wayland, L. [Oth.]: The Cabinet-Maker And Upholsterer's Drawing-Book: In Three Parts (London: Printed For The Author, By T. Bensley; And Sold By J. Mathews ... C. Terry ... J.S. Jordan ... L. Wayland ... And By The Author, 1793)

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on the picture. Thus: the lines 1,3,5,7,4,65 Fig. 2, are all pa-
rallel to each other and to the picture; therefore their repre-
fentations 1,3,5,7, 4,6, on the picture, are all parallel to one
another, as is felf-evident by comparing thefe with their cor-
refponding lines in Fig. 5.
Cafe 4.—If any original line 1, 5, Fig. 2, be perpendicular
to the ground plane, its reprefentation will be perpendicular to
the ground line G R; wherefore the reprefentation of the ori-
ginal 3,7, or any other in the like pofition, lituated any where
on the ground plane, is perpendicular to the ground line G R.
Hence the correfpondent lines 3, 7,1, 5, Fig. 5, are drawn per-
pendicular to G R, the ground line.
From the above theory it may be concluded, that the re-
prefentation of a geometrical fquare or parallelogram *, is a ge-
ometrical fquare or parallelogram, if it be lituated in a plane
parallel to the picture. Hence IK, L M, Fig. 6, is the true re-
prefentation of the original fquare A D, B C, which is in this
pofition.
Cafe 5.—All lines perpendicular to the picture, have their
vanifhing points in the center of the picture.

* See its definition in page 44, and its figure Plate II.

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