Note 11 — TELEPHONIC EXPERIMENTS.

M. Bosscha, who has published in the Archives néerlandaises an interesting paper on the intensity of electric currents in the telephone, says that the minimum intensity of currents necessary to produce a sound in a telephone by the vibration of its diaphragm may be less than 100/1000 of a Daniell element, and the displacement of the centre of the diaphragm would then be invisible. He was unable to measure exactly the range of movements produced in the diaphragm by the influence of the voice, but he believes it to be less than the thousandth part of a millimètre; and from this it follows that, for a sound of 880 vibrations, the intensity of the induced currents developed would be 0·0000792 of the unit of electro-magnetic intensity.