IOWA ACADEMY OF SCIENCES. 49 



SOME OBSERVATIONS UPON THE ACTION OF 



COHERERS WHEN SUBJECTED TO DIRECT 



ELECTROMOTIVE FORCE. 



BY FRANK F. ALMY, 



Most of the earlier quantitative work with coherers 

 seemed to indicate that the coherer was uncertain or 

 indefinite in its action. Some of the more recent work 

 has, however, shown more definite and consistent results. 



The measurements of Gruthe and Trowbridge* on sim- 

 ple coherers subjected to sudden, direct electromotive force 

 tend to show that the current through the coherer increases 

 with the electromotive force in such a way that it would 

 be represented graphically (using e and i as co-ordinates), 

 by a smooth curve which in the limit becomes tangent to 

 a line e = constant. The curves representing the results 

 of their experiments are without abrupt change of curva- 

 ture. 



On the other hand Kinsleyf, subjecting a filing coherer 

 to a continuously varied electromotive force finds "that 

 the resistance remains unchanged, as the potential differ- 

 ence is increased until a certain value is reached, when the 

 resistance suddenly falls." 



In August, 1901, I undertook some measurements upon 

 the behavior of coherers, subjected to a continuously varied 

 electromotive force. The E. M. F. was obtained by a sim- 

 ple potentiometer (Plate XIV), by means of which it could be 

 varied continuously from zero to an\^ desired value. An 

 a,m meter was placed in series with the coherer and a volt- 

 meter in shunt across its terminals. The current flowing 



*Pliys. Rev. 11, p. 22. 

 tPhys. Rev. 12, p. 177. 



