Columbia University Fall Tachistoscope

This device used gravity with or without additional spring tension to move a metal aperture down across a slit in the stationary plate and expose a visual stimulus. The speed of movement of the falling aperture and therefore the exposure time of the stimulus could be measured by timing the closing of electrical contacts which were mounted on the stationary portion of the apparatus. It was manufactured in the machine shop of the Columbia University Psychology Department and carries the engraved words "Columbia University" on its base.