THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE 



[SIXTH SERIES.] S.I 



tt 



MARCH 1901, 



XXIII. An Investigation of the Simple Coherer*. By Philip 



E. Shaw, B.A., B.Sc, Lecturer in Physics in University 

 College, Nottingham f . 



Contents. 



Section. Page 



1. Introductory 265 



2. The Aphometer 266 



3. Dynamical Conditions of the Contacts 268 



4. Pseudo-coherence 271 



5. Direct-current Coherence 274 



6. Coherence Proper 274 



6 a, 6 b, 6 c, 6d. Evidence of ' Orientation ' 275 



7. Dimensions of the ' Bridge ' 280 



8. The Ionic Theory of Conduction 283 



9. Results of other Investigators 284 



10. Various Metals and Carbon 288 



11. Tests with the Electric Micrometer 290 



12. Summary of Results 294 



1. Introductory. 



WHILE investigating telephone relays in the summer of 

 1899, I noticed the following curious effect. A light 

 wire was attached to a galvanometer suspension, so as to 

 move to and fro horizontally with it ; another wire, fixed, 

 was set up outside the galvanometer. When these two wires 

 were made to touch so as to complete a circuit with a current 

 in it, it was found under certain conditions that the wires held 



* By the term " Simple Coherer " is meant one which has only two 

 surfaces in contact. 



f Communicated by the Author. 

 Phil. Mag. S. 6. Vol, 1. No. 3. March 1901. T 



