Tyndall, John, 1820-1893 · London : Longmans, Green · leaf 229
entirely due to the mechanical shaking of the carbons,which, by changing the strength of the current, changescorrespondingly the force of the telephone magnet, causingit, by the varying strength of its attraction, to excitetremors in the thin plate of iron which, in Bells tele-phone, is the… … C is a cylinder of brass having a spiral groove or screwcut upon its surface from end to end. It is mounted uponp spindle (well seen in fig. 109), whose length is rather morethan three times that of the cylinder. At one end of thespindle is a winch handle, between which and the cylfnder THE…
Sound
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