Studie jcdiiodiic.hélio koheieni. 55 



Expérimental Study of a simple Oolierer 



By Trof. Ur. Vladimír Novák and Ph. C. B. Macků. 



Measuring the effect of light on photographie plate by means 

 of the change ofgalvanic conductivity and pontencial différence between 

 the darkned part and the lightened part of the emulsion, onu*j of the 

 authors caught the idea to study this effect with a simple coherer. 

 By „simple" coherer we mean a radioconductor with a single contact. 

 This form of coherers is not yet so studied as it deserved, the arran- 

 gement being usualy such, that différent (mechanical, thermical a. 

 s, o.) disturbances made the changes of résistance of the coherer very 

 uncertain, 



We tried différent forms of the simple coherer and finály found 

 one, which we think to allow to observe différent disturbances, and to 

 be very convenient for the study of the cohereťs phenomenon in 

 generál. 



The section of our coherer is shown in fig. 1. It consists of 

 two électrodes of the samé metal separated by a layer of the halloid 

 of the metal. The cone-shaned cathod floated on raercury in one arm 

 of a U-tubing, being fastened to a glas-rod ground precisely to fit to the 

 walls of the glas-tube. The other électrode in form of a plate was situa- 

 ted eccentrically on the ebonite-covering of the upper-part of the 

 instrument, in order to facilitate the change of the contact on the 

 coherer without changing the pressure. The pressure was due to a 

 column of mercury and water and could be changed by rising or 

 sinking the other tube with mercury, the small changes being produced 

 by means of water. 



*) Ph. Dr. Vladimír Novák „Electric méasurement of the effect of light ou 

 the photographie plate". Věstník král. české společuosti nauk. X. 1902. 



