© Science Museum / Science & Society Picture Library
The Harmonograph was originally invented in the 1870s as a means of analysing vibrations, and was particularly useful for the study of sound. By the time of this example, made by Newton and Co, it was regarded as just a scientific toy for drawing patterns. The pen and drawing table are mounted on pendulums and are set swinging at right angles to each other. The pen is lowered carefully to the table and traces out the resulting combination of the two vibrations. The pendulums can be made to swing more quickly or slowly by altering the number and position of the weights.