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.


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


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