1. telephone, capillary A telephone utilizing electro-capillarity for the production of telephonic effects. The following describes the invention of Antoine Breguet.
The point of a glass tube, drawn out at its lower end to a capillary opening dips vertically into a vessel. This vessel is partly filled with mercury, over which is a layer of dilute sulphuric acid. The end of the immersed tube dips into the acid, but does not reach the mercury. One line contact is with mercury in the tube, the other with the mercury in the vessel. The arrangement of tube and vessel is duplicated, giving one set for each end of the line. On introducing a battery in the circuit the level of the mercury is affected by electro-capillarity. The tubes are closed by plates or diaphragms at their tops, so as to enclose a column of air. It is evident that the pressure of this air will depend upon the level of the mercury in the tube, and this depends on the electro-motive force. On speaking against the diaphragm the sound waves affect the air pressure, and consequently the level, enough to cause potential differences which reproduce the sound in the other instrument.
Definitions of telephone, capillary
