Coherer History of metal filings Cohering Commentary

Edouard Branly electromagnetism

Coherer

• They called them Hertzian waves
• because Heinrich Hertz had discovered them
• and Marconi had not yet invented the radio.
• Edouard Branly was experimenting to see the effects
• of electrical charges and sparks on metal filings,
• and began to make devices containing metal filings
• to detect the presence of electric waves.
• By 1894 people including Oliver Lodge were making
• their Branly coherers to detect Hertzian waves.

History of metal filings

• Even the ancients knew
• magnets attracted metal filings.
• Even before batteries were invented, in 1850,
• Peter Samuel Munk noted that static electricity
• affected the resistance of metal filings.
• Even before Edouard Branly’s work,
• Temistocle Calzecchi-Onesti discovered
• that metal filings between brass plates,
• became conductive when a voltage
• was applied to the plates.

Cohering

• Elements cohere, as did
• the chemicals of life,
• to defy the law of entropy.
• A line composed of points, too
• fine, then too many to count,
• to branch into millions.
• Particules in a brain, we
• don’t know how, arrange
• to form memories and guesses.