apparent direction of eyes in a portrait. 255 
through them. Now, since the upright line ( drawn or sup- 
posed to be drawn on the plane of the picture and repre- 
senting a vertical plane ) will be seen upright, however far 
we move to one side, and will continue to represent a vertical 
plane, it follows that the same set of objects, even in the 
most oblique direction in which the representation can be 
viewed, are still in the same vertical plane, and consequently 
will seem still to be in a line with us, exactly as in the front 
view : seeming as we move, to turn round with us, from 
their first direction, toward any oblique position that we may 
choose to assume. 
In portraits, the phenomena of direction with reference to 
the spectator, and corresponding change of apparent position 
in space when he moves to either side, depend precisely on 
the same principles. A nose drawn directly in front with 
its central line upright, continues directed to the spectator, 
though viewed obliquely. Or, if the right side of the nose 
is represented, it must appear directed to the right of the 
spectator in all situations ; and eyes that turn in a due degree 
from that direction toward the spectator, so as to look at 
him when viewed in front, will continue to do so when 
viewed obliquely. 
As an illustration of the permanent directions of the nose 
and eyes in a portrait, if a compass be represented, Plate XII. 
in front of the picture, in a square box, so placed that the 
sides appear in the same direction as the nose, the needle 
being set parallel to that of the eyes, will represent, in all 
positions from which it can be viewed, a line pointing in their 
apparent direction, and by its permanently vertical position 
will justly exhibit the same appearance which eyes do, of 
