It is composed of an iron cylinder (12.3 cm in length, 10 cm in diameter) fixed to a horizontal shaft, it too made of iron, that passes through the cylinder along its axis and is supported at the ends by two vertical iron supports painted black, fixed to a rectangular wooden platform (35 x 10 cm).
By means of a crank the cylinder can be rotated around its axis and moved about 9 cm along the axis.
If a sheet of paper coated with lampblack is wound on the cylinder and a needle attached to a vibrating system (for example a tuning fork) touches it lightly with the cylinder not in motion and the cylinder is then turned with the crank, the point traces a regular helix on the paper; but if the system is made to vibrate and the oscillations of the needle are parallel to the rotational axis the helix follows a more or less compact zigzag course that reproduces the oscillatory movement of the vibrating system.

Brenni (1986), Vol. I, p. 83
Daguin (1878), T. I, p. 573
Ganot (1864), p. 192

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