880 



Dr. W. H. Eccles on Coherers. 



given to the coherer and the energ}^ passed to the telephone 

 is again a straight line passing some distance from the origin. 



Fig. 6. 





10" 9 Watt 











+ Point Positive 

 * Point Negative 



l'O 











\-. W=5-53xl0" 8 



Vatt 



0-5 











V^^ 











1 __.._ 



- Volt 



0'2 0-4 0-6 0*8 



Iron Point on Oxidized Iron Plate. 



The equation of the curve is 



iv = 0-028 (W- 1-4 xlO" 8 ). 



The curve is the same whether the current passes from point 

 to plate or in the opposite direction, which clearly indicates 

 that the asymmetry of the other curves was due solely to the 

 use of two metals. The curves connecting applied voltage 

 and steady current for these iron point iron plate coherers 

 are also the same whatever the direction of the current. 

 Fig. 7 shows such a curve, which has been selected from a 

 large number as typical. 



A Hypothesis of Coherer Action. 



The experimental results described above lead me to offer a 

 simple hypothesis of the mode of operation of the class of 

 coherers in question. When an oxidized wire is dipped into 

 mercury or touched against a conductor, the oxide dielectric 

 between the conductors is so thin and so extended that a 

 considerable current, relatively speaking, can be passed 

 through it. The films of oxide used in the experiments had 

 a thickness of the order of a wave-'ength of light and an 

 electrical resistance usually between 50 and 2000 ohms. 

 When a current is passed through the film, heat is generated 

 in the film and raises its temperature. The rise of temperature 

 may be considerable if the mass heated is small, but is limited 

 by the escape of heat to the surrounding metal. If the rise 

 of temperature does not affect the resistance of the heated 

 material appreciably, the relation between the applied electro- 

 motive force and the consequent current will be a linear one: 



