As an apparatus capable of exciting interest, probably nothing so
easily constructed surpasses the harmonograph. Your attention will
be completely absorbed in the ever changing, graceful sweep of the
long pendulum, the gyrations of which are faithfully recorded in
the resulting harmonogram.

A careless impetus given to the pendulum may result in a very
beautiful harmonogram, but you may try innumerable times to
duplicate this chance record without success. No two hamonograms
are exactly alike. The harmonograph, while its pendulum swings in
accordance with well known natural laws, is exceedingly erratic
when it comes to obeying any preconceived calculations of its
operator. In this uncertainty lies the charm. If time hangs
heavily or a person is slightly nervous or uneasy, a harmonograph
is a good prescription.

The prime essential in a well working harmonograph is a properly
constructed universal joint. Where such a joint is made with
pivots for its bearings, one pair of pivots are very liable to
have more friction than the other, which retards the movement and
causes the harmonograph to undergo a continuous change of axis. To
obviate this difficulty, the joint should be made similar to those
used on scales. The general appearance of such a joint is shown in
the first illustration, Fig. 1. Stirrups A and B are made of 7/8
by 1/4-in. metal. Holes are drilled in each end of these stirrups
and filed out as shown at C. The two holes shown in the center of
the stirrup A are drilled to fasten the apparatus to the ceiling.
Two corresponding holes are drilled in B to fasten the long
pendulum F to the joint. The cross of the joint D has the ends
shaped as shown at E. The rounded shoulder on E is to prevent the