272 RALPH S. LILLIE AND EARL N. JOHNSTON. 



DESCRIPTION OF PLATE VI. 



FIG. 28. A rusty iron wire forming filaments only on the bright surface from 

 which the rust had been removed. All rust-covered surfaces are cathodic. 



FIG. 29. Both ends of a U-shaped iron wire in a ferricyanide solution. One 

 end is rusted and forms no filaments, the other is polished bright, hence is anodic 

 and forms many filaments. 



FIG. 30. This shows the modification in direction of growth and shape of fila- 

 ments caused by small obstacles (fine sand) in the solution. 



