Cymoscope or Chips? Peculiar terms to describe a device for handling electromagnetic radiation. While the latter is well known nowadays, Cymoscopes - (from the Greek: cyma = waves; scope = see), was not so familiar to the pioneers of radio science. Therefore, in spite of early strange terms or even theories, the scientific understanding of semiconductor materials started by the end of XIX century, when several scientists studied the photovoltaic rectifying effects in chemical compounds and elements like metallic sulphides and Selinium.
In 1874, the German physicist Karl Ferdinand Braun, discovered that certain minerals such as, galena, lead sulphide had the property of unidirectioned conductivity, i.e. allow the passage of A.C. electrical impulses in one direction but inhibit their return surge.
In reality Braun's studies established the rectifying properties of the contact of a metal wire on the surface of mineral galena, creating thus the first metal-semiconducting junction. Fig 243
Based on the research work of Prof. Braun, in 1902 Greenleaf Whittier Pickard discovered the principle of crystal detection. It is indeed very simple as it behaves as a rectifyer, converting high frequency radiation from alternating current to direct current.
Pickard's crystal detector, known as cat's whisker, was manufactured since 1906, when another experimenter, H.H.C. Dundwoody, used this type of detector in a practical way. Fig 244
General Dundwoody while working for the U.S. Army also invented the carborundum radio detector in 1906.
The crystal detector was an innovation in detecting electromagnetic radiation due to its sensitivity as well as practicity. Fig 245
However, considering that it could not amplify signals, its decline began with the development of more reliable termionic devices such as the Fleming diode in 1904, and finally the triode valve invented by Lee de Forest in 1906.

Fig-243 - Principle of metal-semiconducting junction
Fig. 244 - Illustration of Pickard's crystal detector, known as cat's whisker, where:
a) Mineral detector
b) Holder for the mineral detector
c) Metallic contact
Fig. 245 - Illustration of a complete permanent mineral detector, manufactured in England showing its hardware for installing, instruction manual and the cardboard box. A piece of carborundum, the mineral used in the detector construction is seen in the center. General H.H.C. Dundwoody invented the carborundum radio detector in 1906.
Sstudent wireless experiment kit circa 1900, comprising:
- Coherer holder
- Gold leaf electroscope
-Spark gap device
-Carborundum detector and fittings
Fig. 244a - Several types of mineral detectors:
a) and c) differentes types of Galena, Lead Sulphide
c) Commercial type of crystal detector sold under the tradename "Cymosite"
Fig 246 - a typical vintage crystal radio set showing: the crystal set provided with the cat's whisker and the crystal holder, the crystal detector "Cymosite" and the earphone.