| This exhibit
allows the visitor to draw beautiful flowing patterns on a swinging
table. The secret of tuning the drawing board is to get the twisting
frequency to be exactly twice the swinging frequency. The swinging
frequency depends only on the length of the supporting cables and
the twisting frequency depends on the weight on the table. This
exhibit is therefore a combined pendulum. Friction causes the drawn
pattern to slowly get smaller and smaller in a spiral path.