The cards on which designs have
been drawn are in great request, so that the pleasure of the entertainment
does not end with the mere exhibition. An album filled with picked designs,
showing different harmonies and executed in inks of various colours, is a
formidable rival to the choicest results of the amateur photographer's
skill.
Practical Instructions for making Harmonographs.
Pendulums.--For the Rectilinear type of harmonograph wooden rods 5/8 to
3/4 inch in diameter will be found very suitable. They cost about 2d. each.
Be careful to select straight specimens. The upper pendulum of the
Miniature Twin Elliptic type should be of stouter stuff, say a broomstick;
that of the Goold apparatus stouter still.
All pendulums on which weights are slid up and down should be graduated in
inches and fractions, reckoning from the point of suspension as zero. The
graduation makes it easy to re-establish any harmony after the weights have
been shifted.
Suspensions.--For a harmonograph to give satisfaction it is necessary
that very little friction should be set up at the point of suspension, so
that the pendulums may lose amplitude of swing very slowly.
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