Sound / by John Tyndall.

  • Tyndall, John, 1820-1893.
Date:
1883
Catalogue details

Licence: Public Domain Mark

Credit: Sound / by John Tyndall. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    to make the tube swing as a whole. When the vibration is very rapid the ventral segments appear like a series of shadowy spindles, separated from each other by dark mo- tionless nodes. The experiment is a beautiful one, and it is easily performed. If, instead of moving the hand to and fro, it be caused to describe a small circle, the ventral segments become ' surfaces of revolution.' Instead of the hand, moreover, we may employ a hook turned by a whirling-table. Before you is a cord more rigid than the india-rubber tube, 25 feet long, with one of its ends attached to a freely-moving swivel fixed in the ceiling of the room. By turning the whirling-table to which the other end is attached, this cord may be divided into as many as 20 ventral segments, separated from each other by their appropriate nodes. In another arrangement a string of catgut 12 feet long, with silvered beads strung along it, is stretched hori- zontally between a vertical wheel and a free swivel fixed in a rigid stand. On turning the wheel, and properly regulating both the tension and the rapidity of rotation, the beaded cord may be caused to rotate as a whole, and to divide itself successively into 2, 3, 4, or 5 ventral seg- ments. When we envelop the cord in a luminous beam, every spot of light on every bead describes a brilliant circle, and a very beautiful experiment is the result. § 4. Mechanical Illustrations of damping various points of Vibrating Cord. The subject of stationary waves was first experimen- tally treated by the Messrs. Weber, in their excellent re- searches on Wave-motion, published in the ' Wellenlehre.' It is a subject which will well repay your attention by rendering many of the most difficult phenomena of musical strmg3 perfectly intelligible. The connection of both