Light Action in Certain Crystals of Metallic Selenium. 507 



if the same result was obtained as related above. The 

 following table represents the results. 



Table Y. 



Location of 

 light. 



Conductance, 

 C. 



Change in 



Conductance. 



AC. 



Off crystal. 



On end. 



1*5 mm. from end. 



3 „ „ „ 



4-5 „ „ „ 



Between electrodes. 



115 

 130 



125 

 125 

 129 

 209 



5 



10 

 10 

 14 

 94 



Just as previously, the action seems to be transmitted 

 entirely along the crystal. However, in this case the effect 

 is relatively less away from the region of conductivity. A 

 further study of this variation may reveal more exact infor- 

 mation about the nature of the light action in these crystals. 

 It should be pointed out that the pressure of the electrodes 

 on the crystals and the electrical intensity along the crystals 

 alter their conductance. 



It might be asked if this action at a distance might not be 

 ordinary heat action due to the light. This, however, is 

 quite impossible. First, because the action is too rapid. 

 Almost at the very instant the crystal was illuminated the 

 major portion of the conductance change, at a distance away 

 of 10 mm. from the point of illumination, took place. 

 Secondly, by the arragement shown in fig. 4, the conductance 

 was almost doubled by illuminating the end of the crystal. 

 This was too large to be anything but a light effect, for if 

 the light of the same intensity impinged between the elec- 

 trodes, the action was never much greater than this. 



We have thus far shown certain metallic selenium crystals 

 to possess not only the light-electric properties generally 

 recognized in selenium cells (or bridges), but it is shown 

 that they possess a peculiar sympathetic structure limited 

 apparently only by the crystal surfaces. It may be said that 

 we have a new " Action at a distance/' If we can determine 

 the rate of transmission of the action through the crystal, 

 certain information may be obtained as to the nature of the 

 mechanism of transmission. The possible processes that are 

 suggested are, electronic transmission such as exists in the 

 flow of the electric current, transmission by the elastic vibra- 

 tion of the medium, and possibly by the interaction of parts 

 of the atoms moving with velocities approaching that of 



