Howard, Frank: The sketcher's manual: or, the whole art of picture making reduced to the simplest principles by which amateurs may instruct themselves without the aid of a master (London, 1841)

22 PICTORIAL EFFECT.

of the picture should not be light, with the two
sides dark, or with the top and bottom dark
(Plate IX. fig. 2 & 3). But if it form any line,
that must be diagonal. It should appear to come
in at the upper corner on one side, and to go out
at the lower corner on the other (Plate IX.
fig. 1).

As with light so with shadow ; it should
not form a line either vertical or horizontal.
The middle of the picture should not be dark,
with the two sides light, or with the top and
bottom light (Plate IX. fig. 5 & 6) j but the
shadow should run diagonally through the picture
(Plate IX. fig. 4).