214 Dr. J. Moser on the Microphonic 



tion of the energies. The current flowing through a selenium 

 cell experiences a counter force — a polarization. I tried to 

 observe, and, as far as possible, to measure it. This polarization 

 is shown by all my cells and preparations of selenium. I 

 found it, however, when measured by the compensation method, 

 to be only about the thousandth of a volt. In order to ob- 

 serve the polarization as near as possible to its maximum, I 

 employed a rotating switch, which I constructed by means 

 of two alternating tooth-wheels, and which changed the current 

 eighty times per second. 



I next endeavoured to increase the electromotive forces 

 originating in the selenium cell, as well as those produced 

 eventually by light. I tried to attain this by taking the two 

 wires of different material ; then I prepared selenium pieces 

 where selenium was simply between two straight parallel 

 wires. At first I made a selenium cell, just like the one 

 described above, replacing, however, the one copper wire by 

 one of platinum, so that the selenium was between copper and 

 platinum. But the polarization, which again could be easily 

 observed, was here also very small. On measuring, it was 

 found again about one thousandth of a volt. Also this cell 

 did not produce, either in the dark or on illumination, any 

 current which could be observed by the galvanometer. 



In order to increase the polarization, I gave the polarized 

 selenium cell greater capacity. I took, instead of the wires, 

 two larger plates, each 6 centim. long, 3 centim. wide, and 

 about 1 millim. thick. My intention was to begin the expe- 

 riments with three of such pairs, with 



copper, selenium, copper ; 

 zinc, selenium, zinc ; 

 zinc, selenium, copper. 



With the latter of these cells I succeeded (after having sent 

 through it the current of a strong battery) in observing 

 a polarization of about 0*4 volt. The cell had now become a 

 polarization battery, giving rise to a current long after it was 

 separated from the primary battery. 



In all these experiments, and especially in the last, a super- 

 position of polarizations could be distinctly observed ; so that 

 here we have to deal, not simply with thermo-electric currents, 

 but with electro-chemical decomposition. 



An observation, however, which I now made gave a different 

 direction to these researches. But their aim remained un- 

 changed — namely, to explain the efficiency of the selenium cells, 

 to understand the transformation of energy of light into that 

 of sound in the selenium cell, regarding it from a more general 



