IOWA ACADEMY OF SCIENCES. 51 



with the coherer through wires supported independently, 

 dipping one into a mercury cup on the base of the coherer, 

 the second into the vessel of mercury in which the coherer 

 floated, and into which dipped a wire from one terminal of 

 the coherer. The whole apparatus was supported on a 

 stone shelf. The measurements resulted in a family of 

 curves similar to those obtained for the filing coherer, the 

 individual curve depending upon the initial condition of 

 contact. It would appear that the curves given by the 

 measurements of Cluthe and Trowbridge, and those which 

 would represent the behavior of the coherer as described 

 by Kinsley are but widely separated curves of the same 

 family. For, using the filing coherer with a very few 

 filings in a very loose contact, the results conform to those 

 descrilied by Kinsley, while with a large number of filings 

 more closely packed, there is very slight variation of resist- 

 ance with increased electromotive force. Between these 

 two extreme conditions, results which conform to the 

 curves of Guthe and Trowbridge are easily obtained. 



This conclusion is further confirmed by the work of 

 Bose"'' and Ecclest, that has appeared since the above 

 measurements were made. 



If instead of representing the behavior of the coherer 

 graphically in terms of current and E. M. F., we represent 

 the conductivity (reciprocal of resistance) of the coherer 

 as a function of the current flowing, the curve becomes a 

 straight line. A linear relation exists between the condiic- 

 tivitif of tJie coherer and the maximum current that has 

 passed throur/h it. This is expressed by the equasion 



C = Co + Ei (2). 



where C = conductivity of coherer. 



Co = constant depending on initial conditions (initial conduc- 

 tivity) . 



i = Maximum current that has passed through the coherer. 



E^ constant — corresponding to the maximum E.M.F. that 

 the coherer can sustain. 



From the series of simultaneous readings of voltmeter 

 and ammeter the resistance of the coherer was calculated: 



•Electrician, August 30, 1901. 

 t Electrician, August, 1901. 



