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Updated: May 14, 2025
Gas-carbon operates admirably, but the best carbon is that known as willow-charcoal, used by artists in sketching, and when this is impregnated with minute globules of mercury by heating it white-hot and quenching it in liquid mercury, it is in a highly sensitive microphonic condition.
Professor Hughes at length constructed an adjustable hammer-and-anvil microphone of gas-carbon, fixed to the top of a resonating drum, which articulated fairly well, although not so perfectly as a Bell telephone. Perhaps a means of improving both the volume and distinctness of the articulation will yet be forthcoming and we may be able to speak solely by the microphone, if it is found desirable.
This pencil may be of mercurialised charcoal, but the ordinary gas-carbon, which incrusts the interior of the retorts in gas-works, is usually employed. The crayon is supported in an upright position by two little brackets of carbon, hollowed out so as to receive the pointed ends in shallow cups.
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