284 MODERN SCIENCE READER 



nomena, and further migration of the ions, were also con- 

 cerned. For the luminosity increased when the current 

 (of 10 volts, e. g.) was turned on, and the particles were 

 distinctly seen to wander, mostly toward the cathode. If 

 dust granules had alone been at work, the current should 

 gradually have cleared the solution of such granules. But 

 the directed movements were only observed when there was 

 real electrolysis, and no movements and hardly any lumin- 

 osity were seen when the solvent was not water, but a non- 

 electrolyte, like benzol. The bright specks were, moreover, 

 deflected from their rectilinear paths when the cell was 

 placed in a strong magnetic field. On reversing the cur- 

 rent, the bright specks also reversed their movements, which 

 took place at the rate of migrating ions, and on applying 

 alternating currents the particles seemed to be undecided 

 which way to move. 



All these observations appear to indicate that the mov- 

 ing particles are either ions, or other bodies or molecules, 

 drifting together with the ions, and it has long ago been 

 pointed out that the migrating ion would carry some of 

 the solvent with it. The following observations of Kos- 

 sonogow are of particular interest. When a certain critical 

 potential was applied, the number of bright specks suddenly 

 increased very much, and they crowded near the cathode, 

 but a dark space, from 0.05 to 0.08 millimeter in width, was 

 always left close to the cathode. This dark cathode space 

 so well known from experiments on the electric discharge 

 through gases was very well defined, and it was partic- 

 ularly striking when cathodes were used which were not 

 plain, but curved in fanciful ways. The boundary of the 

 dark space always kept parallel to the contours of the 

 cathode. Beyond the dark space the bright particles were 

 in lively motion; but no bright particles crossed the dark 

 space, though the ions must traverse it to be deposited on 

 the cathode. It looked, Kossonogow says, as if the ions lost 

 their luminosity, together with their electric charge, when 

 passing the dark space. When the critical potential 1 



