THE SIMILARITY OF ELECTRICAL PROPERTIES IN LIGHT- 
POSITIVE SELENIUM TO THOSE IN CERTAIN 
CRYSTAL CONTACTS * 
BY F. C. BROWN. 
Many of the phenomena having to do with the electrical properties 
of selenium have been regarded as almost unique. Likewise many of 
the phenomena appearing in connection with the resistance of crystal 
contacts are considered as unique. Neither of the above sets of phe- 
nomena have been explained from a sufficiently simple and satisfactory 
basis. 
It is therefore believed that certain striking similarities in the two 
above sets of phenomena are significant. The organization of facts in 
this paper will make it rather convenient to assume that the major por- 
tion of the resistance in light-sensitive selenium is of a like nature to 
the resistance in crystal contacts. The essential phenomena to which 
attention may be called are as follows : 
1. The variation of the resistance with pressure. 
2. The apparent invalidity of Ohm’s law. 
3. The change of resistance with the time of current action. 
4. The effect of slight amalgamation. 
5. The effect of abrasion. 
6. The effect of alternating currents. 
7. The breaking down of the resistance by high voltage. 
8. The unlikeness of light action. 
GENERAL CONSIDERATIONS. 
The variations of resistance to be compared appear under apparently 
different circumstances. In crystal contacts the experiments were usually 
carried out with a simple crystal in contact with various metals. The 
surface and manner of contact has been varied in many ways, by using 
points, and contact surfaces of varying dimensions and treatment. But 
with selenium the case is more complicated, the crystals are of a very 
large number and not all of one kind. The current of electricity in 
selenium must pass through many contacts in series and in multiple 
*Paper before A. A. A. S., December, 1912. 
