the appearance of movement effects which do not correspond to an
objective motion. The impression of backward movement can arise from
forward motions, quick movement from slow, complete rest from
combinations of movements. For the first time the impression of movement
was synthetically produced from different elements. For those who fancy
that the "new psychology" with its experimental analysis of
psychological experiences began only in the second half of the
nineteenth century or perhaps even with the foundation of the
psychological laboratories, it might be enlightening to study those
discussions of the early thirties.

The next step leads us much further. In the fall of 1832 Stampfer in
Germany and Plateau in France, independent of each other, at the same
time designed a device by which pictures of objects in various phases of
movement give the impression of continued motion. Both secured the
effect by cutting fine slits in a black disk in the direction of the
radius. When the disk is revolved around its center, these slits pass
the eye of the observer. If he holds it before a mirror and on the rear
side of the disk pictures are drawn corresponding to the various slits,
the eye will see one picture after another in rapid succession at the
same place. If these little pictures give us the various stages of a
movement, for instance a wheel with its spokes in different positions,
the whole series of impressions will be combined into the perception of
a revolving wheel. Stampfer called them the stroboscopic disks, Plateau
the phenakistoscope. The smaller the slits, the sharper the pictures.
Uchatius in Vienna constructed an apparatus as early as 1853 to throw
these pictures of the stroboscopic disks on the wall. Horner followed
with the daedaleum, in which the disk was replaced by a hollow cylinder
which had the pictures on the inside and holes to watch them from
without while the cylinder was in rotation. From this was developed the