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Updated: May 26, 2025
The tube was fastened with sealing-wax, and with it I got excellent speech heard in a Bell receiver. I tried putting in a large number of these tubes, all in quantity, on the bottom of a ferrotype plate, but with no advantage.
The most distinct articulate speech was obtained from an ordinary ferrotype telephone plate, secured at the edges, and one of the glass tubes you see here attached to it. Mr. J. Munro, whose name is well known not only as a very clear writer upon electrical subjects, but as an original investigator, has recently, with the assistance of Mr.
I then tried mounting a tube on the end of a speaking-trumpet and speaking to the mercury, but got no effect. In every place where I attached the glass tube itself to a sounding-board I got a very accurate reproduction. I put one on a piece of ferrotype plate, and that gave really the best result I ever got.
Any work which is to be reproduced many times, such as postage stamps and parts of bank-notes, is made on small pies of steel called dies. If the design to be used is in the shape of a drawing or engraving, a sheet of gelatin may be laid over it and the outlines traced with a sharp-pointed instrument. More often a photograph is taken on a ferrotype plate and the outlines scratched into the plate.
The primitive telephone has been greatly improved, the double electro-magnet being replaced by a single bar magnet having a small coil or bobbin of fine wire surrounding one pole, in front of which a thin disc of ferrotype is fixed in a circular mouthpiece, and serves as a combined membrane and armature.
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