THE MYSTERIOUS CRYSTAL

Daily Telegraph (Napier), Volume 58, Issue 215, 11 October 1929, Page 4

THE MYSTERIOUS CRYSTAL

I11 spite of prolonged research the actual "mechanism" of the crystal detector is still lavgely a matter of conjecture. In point of fact the crystal is onlv one example of a large class of "rectifiers," all more or less mysterious in their action. So far as electrolytic rectifiers are concerned we know that a layer of oxide is formed when the current passes in one direction so as to obstruct any further flow, while- n.o such layer occurs when the current is reversed. The theory of crystal rectification most widely accepted depends upon thermo-electric Action and the settingup of a potential difference in oue direction across the point of contact due to a combination of the Joule, Seebeck, and Peltier effects. It is claimed, however, that this explanation can no longer liolrl good in view of the discovery that crystals are capable of rectifying alternating currents of a frequency of over ten million cycles a secnnd and of the order of micro-amps. It is hardly conceivahle that thermoelectric or even chemical changes could take place at such a rate.