1874,1904

Crystal diode

• Karl Ferdinand Braun discovered
• unilateral conduction of crystals in 1874
• and patented a cat’s-whisker crystal diode
• as a radio rectifier in 1899.
• Braun found that the point of a wire
• that lightly touches a semiconducting crystal
• creates a junction that permits electrons
• to flow from the wire to the crystal
• but not from the crystal to the wire.
• Around 1904, Henry Harrison Chase Dunwoody
• developed a cat’s-whisker detector using carborundum,
• and Greenleaf Whittier Pickard developed
• a cat’s-whisker detector using galena.

Cat’s-whisker detector

• Different crystals made cat’s-whisker detectors—silicon,
• carborundum, galena, molybdenite, iron pyrite, iron disulfide.
• Some galena crystals made good detectors,
• and some didn’t no matter how you adjusted them.
• Generally, the magic wasn’t in the type of crystal;
• it was in finding the right pressure and point of contact.
• The fine point of the wire had to touch the crystal gently
• and some positions on the crystal wouldn’t work at all.

Crystal divination

• The power of crystals
• to orient the mind
• precedes discovery
• of its electromagnetic effects.
• Listen carefully
• to the inside a seashell.
• It does indeed seem
• like the sound of the sea.