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Primary sourcePainting8 March 1876

Drawing of a Liquid Transmitter, 8 March 1876

Alexander Graham Bell · 8 March 1876

Bell's witnessed sketch of his liquid transmitter design, central to his priority dispute with Elisha Gray.

Bell's own technical sketch, witnessed at the time, used as evidence in his priority dispute over the telephone.

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Handwritten pen sketch labeled 'Fig 4' in a notebook showing a liquid transmitter: a diaphragm labeled B, a cup labeled C in a container, a point labeled P, a battery symbol, and a switch labeled S, with partial handwritten text below.
Alexander Graham Bell, liquid transmitter sketch, 8 March 1876. Notebook page.

About this source

What it is

This is a pen sketch by Alexander Graham Bell, labeled "Fig 4," showing a liquid transmitter design with a diaphragm, a cup, a point, a battery, and a switch. It comes from Bell's notebook of early 1876 and was signed by witnesses who initialed it at the time.

Why it matters

This drawing documents Bell's experiments with variable-resistance liquid transmitters just before his famous telephone breakthrough. Because it was witnessed and dated, it became important evidence in the legal dispute over whether Bell or rival inventor Elisha Gray deserved credit for key telephone technology.

Look closer

  • Why might Bell have had other people initial his notebook pages?
  • What can a technical sketch tell you that written words alone cannot?
  • Why would a dated and witnessed drawing matter so much in a legal dispute?

This painting is part of the curated material that grounds the AI version of Alexander Graham on Humy.ai — when students ask about related events, the AI can quote it and cite it.

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