Abstract
LONDON. Physical Society, December II.—Mr. James Swinburne, vice-president, in the chair.—A method of mechanically reinforcing sounds, by the Rev. T. C. Porter. If a tuning-fork be sounded and placed in a flame, there is a very marked reinforcement of the sound. This is proved not to be due to resonance in the ordinary sense, but to the change from continuous to intermittent combustion. In certain circumstances the impulses given to the air external to the flame, by the waves of burning gas, are more forcible than those given by the unaided sounding body. Thus a new way of reinforcing the sounds given by a vibrating body is found, and the rest of the paper demonstrates this for the phonograph, a flame being used instead of the ordinary trumpet. Coal-gas and air are brought by tubes into the chamber of the “reproducer” and thence to a jet, where they are burnt. The vibrations of the reproducer are thus impressed on the issuing gas and air, which burn synchronously with them, the sounds thus emitted being easily heard over a large room. In practice it is found best to spread out the flame by a second jet of air, or of mixed air and gas, placed close to the first jet and at right angles to it. The author describes the nature and quality of the sounds emitted by the flame, and the modifications of these which may be produced.—The Simmance-Abady “flickerp” photometer, by Messrs. Simmance and Abady. The principle of the flicker photometer, discovered by Prof. O. N. Rood ten years ago, has frequently been remarked on, but attempts to design a trustworthy apparatus depending upon this principle have hitherto been unsuccessful. The authors, guided by the following rules, have designed a photometer which is capable of balancing and comparing the most violently contrasted tints:—The light-effects must be in juxtaposition without any apparent division line, and must move, oscillate, or rotate so that the point of juncture of the rays of the two lights passes and returns entirely across the vision field. Any hiatus, or longer exhibition of one light than the other, biases the result. The observation surfaces, or surfaces upon which the light rays fall, must be at exactly the same distance from the eye, at exactly the same angle in relation to the line of sight, and must be of pure white, such as is afforded, for example, by a clean chalk, plaster of Paris, magnesium carbonate, or barium sulphate; any tint affects the accuracy of the result. The observation surfaces must also themselves in turn occupy the field of vision; an apparent movement or optical illusion does not afford accurate results.—Mr. Rollo Appleyarrd exhibited a “conductometer” the theory and mechanical details of which are fully described in the Proceedings of the Institution of Civil Engineers, vol. cliv., session 1902-3, part iv.—Prof. L. R. Wilberforce exhibited a model to illustrate various properties of wave-motion. The model consists of a series of brass balls suspended in a line by spiral springs and capable of transverse or up and down motion. The balls can be set in vibration by releasing them from extreme positions by means of triggers, one set of triggers controlling the up and down motion, and another set the pendular.
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Societies and Academies . Nature 69, 164–168 (1903). https://doi.org/10.1038/069164a0
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DOI: https://doi.org/10.1038/069164a0