The Pseudoscope creates one of the most remarkable of all
optical illusions, and was first described by Sir Charles
Wheatstone in the 1830s. The Pseudoscope swaps the incoming
images, so that the right eye sees what the left eye would have
seen, and vice versa. The pseudoscope therefore does to front
and back what a mirror does to left and right. This means that
foreground becomes background and visible background becomes
foreground, or more simply, background advances, foreground
recedes. When you view objects with this scope, the convex
becomes concave. A tree turns inside out as it were - it's front
branches appear at the back, whilst the back branches come out
in front, hanging or suspended in mid-air as their support is
eclipsed by branches in front. The scope will suggest to the
viewer that a person's face is hollow or concave but your brain
refuses to accept such nonsence and so peoples' heads merely
appear odd or uncomfortable to look at. It is best then to
choose to look at a landscape or tree or any